---
type: "resource-definitions"
title: "CodeSystem Definitions"
resource: "CodeSystem"
---
# CodeSystem Definitions
## CodeSystem
Declares the existence of and describes a code system or code system supplement
**Definition:** The CodeSystem resource is used to declare the existence of and describe a code system or code system supplement and its key properties, and optionally define a part or all of its content.
**Cardinality:** 0..*
**Constraints:** csd-1 | error | Within a code system definition, all the codes SHALL be unique | concept.exists() implies concept.code.combine(%resource.concept.descendants().concept.code).isDistinct(); csd-2 | warning | If there is an explicit hierarchy, a hierarchyMeaning should be provided | concept.concept.exists() implies hierarchyMeaning.exists(); csd-3 | warning | If there is an implicit hierarchy, a hierarchyMeaning should be provided | concept.where(property.code = 'parent' or property.code = 'child').exists() implies hierarchyMeaning.exists(); csd-4 | error | If the code system content = supplement, it must nominate what it's a supplement for | CodeSystem.content = 'supplement' implies CodeSystem.supplements.exists(); csd-7 | warning | caseSensitive SHOULD be provided | caseSensitive.exists(); cnl-0 | warning | Name should be usable as an identifier for the module by machine processing applications such as code generation | name.exists() implies name.matches('^[A-Z]([A-Za-z0-9_]){1,254}$')
**Mappings:** rim=N/A; w5=conformance.terminology
## CodeSystem.url
Canonical identifier for this code system, represented as a URI (globally unique) (Coding.system)
**Definition:** An absolute URI that is used to identify this code system when it is referenced in a specification, model, design or an instance; also called its canonical identifier. This SHOULD be globally unique and SHOULD be a literal address at which an authoritative instance of this code system is (or will be) published. This URL can be the target of a canonical reference. It SHALL remain the same when the code system is stored on different servers. This is used in [Coding](datatypes.html#Coding).system.
**Comments:** Can be a urn:uuid: or a urn:oid: but real http: addresses are preferred. Multiple instances may share the same URL if they have a distinct version.
The determination of when to create a new version of a resource (same url, new version) vs. defining a new artifact is up to the author. Considerations for making this decision are found in [Technical and Business Versions](resource.html#versions).
In some cases, the resource can no longer be found at the stated url, but the url itself cannot change. Implementations can use the [meta.source](resource.html#meta) element to indicate where the current master source of the resource can be found.
**Requirements:** Allows the code system to be referenced by a single globally unique identifier.
**Cardinality:** 0..1
**Type:** [uri](/uri)
**Summary:** true
**Constraints:** cnl-1 | warning | URL should not contain | or # - these characters make processing canonical references problematic | exists() implies matches('^[^|# ]+$')
**Mappings:** w5=FiveWs.identifier
## CodeSystem.identifier
Additional identifier for the code system (business identifier)
**Definition:** A formal identifier that is used to identify this code system when it is represented in other formats, or referenced in a specification, model, design or an instance.
**Requirements:** Allows externally provided and/or usable business identifiers to be easily associated with the module.
**Cardinality:** 0..*
**Type:** [Identifier](/Identifier)
**Summary:** true
**Mappings:** w5=FiveWs.identifier; objimpl=no-gen-base
## CodeSystem.version
Business version of the code system (Coding.version)
**Definition:** The identifier that is used to identify this version of the code system when it is referenced in a specification, model, design or instance. This is an arbitrary value managed by the code system author and is not expected to be globally unique. For example, it might be a timestamp (e.g. yyyymmdd) if a managed version is not available. There is also no expectation that versions can be placed in a lexicographical sequence. This is used in [Coding](datatypes.html#Coding).version.
**Comments:** There may be different code system instances that have the same identifier but different versions. The version can be appended to the url in a reference to allow a reference to a particular business version of the code system with the format [url]|[version]. The version SHOULD NOT contain a '#' - see [Business Version](resource.html#bv-format).
**Cardinality:** 0..1
**Type:** [string](/string)
**Summary:** true
**Mappings:** w5=FiveWs.version
## CodeSystem.versionAlgorithm[x]
How to compare versions
**Definition:** Indicates the mechanism used to compare versions to determine which CodeSystem is more current.
**Comments:** If set as a string, this is a FHIRPath expression that has two additional context variables passed in - %version1 and %version2 and will return a negative number if version1 is newer, a positive number if version2 and a 0 if the version ordering can't be successfully be determined.
**Cardinality:** 0..1
**Type:** [string](/string), [Coding](/Coding)
**Binding:** extensible:[version-algorithm](/valueset-version-algorithm)
**Summary:** true
## CodeSystem.name
Name for this code system (computer friendly)
**Definition:** A natural language name identifying the code system. This name should be usable as an identifier for the module by machine processing applications such as code generation.
**Comments:** The name is not expected to be globally unique. The name should be a simple alphanumeric type name to ensure that it is machine-processing friendly.
**Requirements:** Support human navigation and code generation.
**Conditions:** cnl-0
**Cardinality:** 0..1
**Type:** [string](/string)
**Summary:** true
## CodeSystem.title
Name for this code system (human friendly)
**Definition:** A short, descriptive, user-friendly title for the code system.
**Comments:** This name does not need to be machine-processing friendly and may contain punctuation, white-space, etc.
**Cardinality:** 0..1
**Type:** [string](/string)
**Summary:** true
## CodeSystem.status
draft | active | retired | unknown
**Definition:** The status of this code system. Enables tracking the life-cycle of the content.
**Comments:** Allows filtering of code systems that are appropriate for use versus not.
See guidance around (not) making local changes to elements [here](canonicalresource.html#localization).
**Cardinality:** 1..1
**Type:** [code](/code)
**Binding:** required:[publication-status](/valueset-publication-status)
**Summary:** true
**Is Modifier:** true (Reason: This is labeled as "Is Modifier" because applications should not use a retired CodeSystem without due consideration)
**Mappings:** w5=FiveWs.status
## CodeSystem.experimental
For testing only - never for real usage
**Definition:** A Boolean value to indicate that this code system is authored for testing purposes (or education/evaluation/marketing) and no version of this resource will ever be intended for genuine usage.
**Comments:** Allows filtering of code systems that are appropriate for use versus not.. Experimental resources might include example instances in implementation guides, instances created solely for testing purposes, etc. If experimental is 'true' for any version of a resource, it should be true for all versions of the resource. (If experimental changes, then it is being misused or a resource that was never intended for real-world use has unexpectedly changed its purpose.).
Experimental resources are not expected to be stable and may well have breaking changes without a corresponding change to the 'version' element.
**Requirements:** Enables experimental content to be developed following the same lifecycle that would be used for a production-level code system.
**Meaning if Missing:** If absent, this resource is treated as though it is not experimental.
**Cardinality:** 0..1
**Type:** [boolean](/boolean)
**Summary:** true
**Mappings:** w5=FiveWs.class
## CodeSystem.date
Date last changed
**Definition:** The date (and optionally time) when the code system was last significantly changed. The date must change when the business version changes and it must change if the status code changes. In addition, it should change when the substantive content of the code system changes.
**Comments:** The date is often not tracked until the resource is published, but may be present on draft content. Note that this is not the same as the resource last-modified-date, since the resource may be a secondary representation of the code system. Additional specific dates may be added as extensions or be found by consulting Provenances associated with past versions of the resource.
See guidance around (not) making local changes to elements [here](canonicalresource.html#localization).
**Aliases:** Revision Date
**Cardinality:** 0..1
**Type:** [dateTime](/dateTime)
**Summary:** true
**Mappings:** w5=FiveWs.recorded
## CodeSystem.publisher
Name of the publisher/steward (organization or individual)
**Definition:** The name of the organization or individual responsible for the release and ongoing maintenance of the code system.
**Comments:** Usually an organization but may be an individual. The publisher (or steward) of the code system is the organization or individual primarily responsible for the maintenance and upkeep of the code system. This is not necessarily the same individual or organization that developed and initially authored the content. The publisher is the primary point of contact for questions or issues with the code system. This item SHOULD be populated unless the information is available from context.
**Requirements:** Helps establish the "authority/credibility" of the code system. May also allow for contact.
**Cardinality:** 0..1
**Type:** [string](/string)
**Summary:** true
**Mappings:** w5=FiveWs.witness
## CodeSystem.contact
Contact details for the publisher
**Definition:** Contact details to assist a user in finding and communicating with the publisher.
**Comments:** May be a web site, an email address, a telephone number, etc.
See guidance around (not) making local changes to elements [here](canonicalresource.html#localization).
**Cardinality:** 0..*
**Type:** [ContactDetail](/ContactDetail)
**Summary:** true
## CodeSystem.description
Natural language description of the code system
**Definition:** A free text natural language description of the code system from a consumer's perspective.
**Comments:** This description can be used to capture details such as comments about misuse, instructions for clinical use and interpretation, literature references, examples from the paper world, etc. It is not a rendering of the code system as conveyed in the 'text' field of the resource itself. This item SHOULD be populated unless the information is available from context (e.g. the language of the code system is presumed to be the predominant language in the place the code system was created).
**Aliases:** Scope, Purpose
**Cardinality:** 0..1
**Type:** [markdown](/markdown)
**Mappings:** rim=N/A
## CodeSystem.useContext
The context that the content is intended to support
**Definition:** The content was developed with a focus and intent of supporting the contexts that are listed. These contexts may be general categories (gender, age, ...) or may be references to specific programs (insurance plans, studies, ...) and may be used to assist with indexing and searching for appropriate code system instances.
**Comments:** When multiple useContexts are specified, there is no expectation that all or any of the contexts apply.
**Requirements:** Assist in searching for appropriate content.
**Cardinality:** 0..*
**Type:** [UsageContext](/UsageContext)
**Summary:** true
## CodeSystem.jurisdiction
Jurisdiction of the authority that maintains the code system (if applicable)
**Definition:** A legal or geographic region in which the authority that maintains the resource is operating. In general, the jurisdiction is also found in the useContext. The useContext may reference additional jurisdictions because the defining jurisdiction does not necessarily limit the jurisdictions of use.
**Comments:** It may be possible for the code system to be used in jurisdictions other than those for which it was originally designed or intended.
DEPRECATION NOTE: For consistency, implementations are encouraged to migrate to using the new 'jurisdiction' code in the useContext element. (I.e. useContext.code indicating http://terminology.hl7.org/CodeSystem/usage-context-type#jurisdiction and useContext.valueCodeableConcept indicating the jurisdiction.)
**Cardinality:** 0..*
**Type:** [CodeableConcept](/CodeableConcept)
**Binding:** extensible:[jurisdiction](/valueset-jurisdiction)
**Summary:** true
## CodeSystem.purpose
Why this code system is defined
**Definition:** Explanation of why this code system is needed and why it has been designed as it has.
**Comments:** This element does not describe the usage of the code system. Instead, it provides traceability of ''why'' the resource is either needed or ''why'' it is defined as it is. This may be used to point to source materials or specifications that drove the structure of this code system.
**Cardinality:** 0..1
**Type:** [markdown](/markdown)
**Mappings:** w5=FiveWs.why[x]; objimpl=no-gen-base
## CodeSystem.copyright
Notice about intellectual property ownership, can include restrictions on use
**Definition:** A copyright statement relating to the code system and/or its contents. Copyright statements are notices of intellectual property ownership and can include restrictions on the use and publishing of the code system.
**Comments:** ... Sometimes, the copyright differs between the code system and the codes that are included. The copyright statement should clearly differentiate between these when required.
**Requirements:** Consumers must be able to determine any legal restrictions on the use of the code system and/or its content.
**Aliases:** License, Restrictions
**Cardinality:** 0..1
**Type:** [markdown](/markdown)
**Mappings:** objimpl=no-gen-base
## CodeSystem.copyrightLabel
Copyright holder and year(s)
**Definition:** A short string (<50 characters), suitable for inclusion in a page footer that identifies the copyright holder, effective period, and optionally whether rights are restricted. (e.g. 'All rights reserved', 'Some rights reserved').
**Comments:** The copyright symbol and the '(c)' textual representation SHOULD NOT be included in this string. It will be added by software when rendering the notation. Full details about licensing, restrictions, warrantees, etc. goes in the more general 'copyright' element.
**Requirements:** Defines the content expected to be rendered in all representations of the artifact.
**Cardinality:** 0..1
**Type:** [string](/string)
## CodeSystem.approvalDate
When the CodeSystem was approved by publisher
**Definition:** The date on which the resource content was approved by the publisher. Approval happens once when the content is officially approved for usage.
**Comments:** The 'date' element may be more recent than the approval date because of minor changes or editorial corrections.
See guidance around (not) making local changes to elements [here](canonicalresource.html#localization).
**Cardinality:** 0..1
**Type:** [date](/date)
**Mappings:** objimpl=no-gen-base
## CodeSystem.lastReviewDate
When the CodeSystem was last reviewed by the publisher
**Definition:** The date on which the resource content was last reviewed. Review happens periodically after approval but does not change the original approval date.
**Comments:** If specified, this date follows the original approval date.
See guidance around (not) making local changes to elements [here](canonicalresource.html#localization).
**Requirements:** Gives a sense of how "current" the content is. Resources that have not been reviewed in a long time may have a risk of being less appropriate/relevant.
**Cardinality:** 0..1
**Type:** [date](/date)
**Mappings:** objimpl=no-gen-base
## CodeSystem.effectivePeriod
When the CodeSystem is expected to be used
**Definition:** The period during which the CodeSystem content was or is planned to be in active use.
**Comments:** The effective period for a CodeSystem determines when the content is applicable for usage and is independent of publication and review dates. For example, a system intended to be used for the year 2016 might be published in 2015.
See guidance around (not) making local changes to elements [here](canonicalresource.html#localization).
**Requirements:** Allows establishing a transition before a resource comes into effect and also allows for a sunsetting process when new versions of the CodeSystem are or are expected to be used instead.
**Cardinality:** 0..1
**Type:** [Period](/Period)
**Summary:** true
**Mappings:** objimpl=no-gen-base
## CodeSystem.topic
E.g. Education, Treatment, Assessment, etc
**Definition:** Descriptions related to the content of the CodeSystem. Topics provide a high-level categorization as well as keywords for the CodeSystem that can be useful for filtering and searching.
**Comments:** DEPRECATION NOTE: For consistency, implementations are encouraged to migrate to using the new 'topic' code in the useContext element. (I.e. useContext.code indicating http://terminology.hl7.org/CodeSystem/usage-context-type#topic and useContext.valueCodeableConcept indicating the topic)
**Requirements:** Repositories must be able to determine how to categorize the CodeSystem so that it can be found by topical and keyword searches.
**Cardinality:** 0..*
**Type:** [CodeableConcept](/CodeableConcept)
**Binding:** example:[definition-topic](/valueset-definition-topic)
## CodeSystem.author
Who authored the CodeSystem
**Definition:** An individiual or organization primarily involved in the creation and maintenance of the CodeSystem.
**Cardinality:** 0..*
**Type:** [ContactDetail](/ContactDetail)
## CodeSystem.editor
Who edited the CodeSystem
**Definition:** An individual or organization primarily responsible for internal coherence of the CodeSystem.
**Cardinality:** 0..*
**Type:** [ContactDetail](/ContactDetail)
## CodeSystem.reviewer
Who reviewed the CodeSystem
**Definition:** An individual or organization asserted by the publisher to be primarily responsible for review of some aspect of the CodeSystem.
**Comments:** See guidance around (not) making local changes to elements [here](canonicalresource.html#localization).
**Cardinality:** 0..*
**Type:** [ContactDetail](/ContactDetail)
## CodeSystem.endorser
Who endorsed the CodeSystem
**Definition:** An individual or organization asserted by the publisher to be responsible for officially endorsing the CodeSystem for use in some setting.
**Comments:** See guidance around (not) making local changes to elements [here](canonicalresource.html#localization).
**Cardinality:** 0..*
**Type:** [ContactDetail](/ContactDetail)
## CodeSystem.relatedArtifact
Additional documentation, citations, etc
**Definition:** Related artifacts such as additional documentation, justification, dependencies, bibliographic references, and predecessor and successor artifacts. If the type is `successor` or `predecessor`, the related resource must be a CodeSystem.
**Comments:** Each related artifact is either an attachment, or a reference to another resource, but not both.
**Requirements:** A CodeSystem must be able to provide enough information for consumers of the content (and/or interventions or results produced by the content) to be able to determine and understand the justification for and evidence in support of the content.
**Cardinality:** 0..*
**Type:** [RelatedArtifact](/RelatedArtifact)
**Constraints:** csd-8 | error | Related artifact can't be depends-on or composed-of | (type in ('depends-on' | 'composed-of')).not()
## CodeSystem.caseSensitive
If code comparison is case sensitive
**Definition:** If code comparison is case sensitive when codes within this system are compared to each other.
**Comments:** If this value is missing, then it is not specified whether a code system is case sensitive or not. When case sensitivity is not known, systems SHOULD produce codes with the correct case, and treat codes as case-sensitive, since this will mean any incorrect interpretation of codes is not a silent failure. This element is primarily provided to support validation software. Case-insensitive comparisons do not take locale into account, and will result in unsatisfactory results for certain locales. Character case definitions and conversions are out of scope for the FHIR standard, and the results of such operations are implementation dependent.
**Cardinality:** 0..1
**Type:** [boolean](/boolean)
**Summary:** true
## CodeSystem.valueSet
Canonical reference to the value set with entire code system
**Definition:** Canonical reference to the value set that contains all codes in the code system independent of code status.
**Comments:** The definition of the value set SHALL include all codes from this code system, independent of concept status, and only codes from this code system. It SHALL be immutable, and operations SHOULD support validation of any allowed code compositions.
**Cardinality:** 0..1
**Type:** [canonical](/canonical)
**Summary:** true
## CodeSystem.hierarchyMeaning
grouped-by | is-a | part-of | classified-with
**Definition:** The meaning of the hierarchy of concepts as represented in this resource.
**Comments:** Note that other representations might have a different hierarchy or none at all, and represent the information using properties.
**Conditions:** csd-2, csd-3
**Cardinality:** 0..1
**Type:** [code](/code)
**Binding:** required:[codesystem-hierarchy-meaning](/valueset-codesystem-hierarchy-meaning)
**Summary:** true
## CodeSystem.compositional
If code system defines a compositional grammar
**Definition:** The code system defines a compositional (post-coordination) grammar.
**Comments:** Note that the code system resource does not define what the compositional grammar is, only whether or not there is one. Note that the code system resource does not define what the compositional grammar is, only whether or not there is one. Review the Using Code System X with HL7 Standards (where Code System X is a specific code system) pages at [terminology.hl7.org](https://terminology.hl7.org/external_code_systems.html) to learn about a code system's post coordination support. [Coding.code](datatypes-definitions.html#Coding.code) has some more information about how a post coordinated expression may be exchanged in a code element.
**Aliases:** grammar
**Cardinality:** 0..1
**Type:** [boolean](/boolean)
**Summary:** true
## CodeSystem.versionNeeded
If definitions are not stable
**Definition:** This flag is used to signify that the code system does not commit to concept permanence across versions. If true, a version must be specified when referencing this code system.
**Comments:** Best practice is that code systems do not redefine concepts, or that if concepts are redefined, a new code system definition is created. But this is not always possible, so some code systems may be defined as 'versionNeeded'.
Most code systems occasionally refine the displays defined for concepts between versions. Contexts in which the concept display values are validated may require that the version be specified for some code systems irrespective of the value of this property.
**Cardinality:** 0..1
**Type:** [boolean](/boolean)
**Summary:** true
## CodeSystem.content
not-present | example | fragment | complete | supplement
**Definition:** The extent of the content of the code system (the concepts and codes it defines) are represented in this resource instance.
**Conditions:** csd-4
**Cardinality:** 1..1
**Type:** [code](/code)
**Binding:** required:[codesystem-content-mode](/valueset-codesystem-content-mode)
**Summary:** true
## CodeSystem.supplements
Canonical URL of Code System this adds designations and properties to
**Definition:** The canonical URL of the code system that this code system supplement is adding designations and properties to.
**Comments:** The most common use of a code system supplement is to add additional language support.
**Conditions:** csd-4
**Cardinality:** 0..1
**Type:** [canonical](/canonical)
**Summary:** true
## CodeSystem.count
Total concepts in the code system
**Definition:** The total number of concepts defined by the code system. Where the code system has a compositional grammar, the basis of this count is defined by the system steward.
**Comments:** The count of concepts defined in this resource cannot be more than this value but may be less for several reasons - see the content element.
**Cardinality:** 0..1
**Type:** [unsignedInt](/unsignedInt)
**Summary:** true
## CodeSystem.filter
Filter that can be used in a value set
**Definition:** A filter that can be used in a value set compose statement when selecting concepts using a filter.
**Comments:** Note that filters defined in code systems usually require custom code on the part of any terminology engine that will make them available for use in value set filters. For this reason, they are generally only seen in high value published terminologies.
**Cardinality:** 0..*
**Type:** [BackboneElement](/BackboneElement)
**Summary:** true
## CodeSystem.filter.code
Code that identifies the filter
**Definition:** The code that identifies this filter when it is used as a filter in [ValueSet](valueset.html#).compose.include.filter.
**Cardinality:** 1..1
**Type:** [code](/code)
**Summary:** true
## CodeSystem.filter.description
How or why the filter is used
**Definition:** A description of how or why the filter is used.
**Cardinality:** 0..1
**Type:** [string](/string)
**Summary:** true
## CodeSystem.filter.operator
= | is-a | descendent-of | is-not-a | regex | in | not-in | generalizes | child-of | descendent-leaf | exists
**Definition:** A list of operators that can be used with the filter.
**Cardinality:** 1..*
**Type:** [code](/code)
**Binding:** required:[filter-operator](/valueset-filter-operator)
**Summary:** true
## CodeSystem.filter.value
What to use for the value
**Definition:** A description of what the value for the filter should be.
**Cardinality:** 1..1
**Type:** [string](/string)
**Summary:** true
## CodeSystem.property
Additional information supplied about each concept
**Definition:** A property defines an additional slot through which additional information can be provided about a concept.
**Comments:** Multiple occurrences of CodeSystem.concept.property may occur for a CodeSystem.property where CodeSystem.concept.property.code is the same and CodeSystem.concept.property.value differs. For example: multiple designations for a single concept.
**Cardinality:** 0..*
**Type:** [BackboneElement](/BackboneElement)
**Summary:** true
## CodeSystem.property.code
Identifies the property on the concepts, and when referred to in operations
**Definition:** A code that is used to identify the property. The code is used internally (in CodeSystem.concept.property.code) and also externally, such as in property filters.
**Cardinality:** 1..1
**Type:** [code](/code)
**Summary:** true
## CodeSystem.property.uri
Formal identifier for the property
**Definition:** Reference to the formal meaning of the property. One possible source of meaning is the [Concept Properties](codesystem-concept-properties.html) code system.
**Cardinality:** 0..1
**Type:** [uri](/uri)
**Summary:** true
## CodeSystem.property.description
Why the property is defined, and/or what it conveys
**Definition:** A description of the property- why it is defined, and how its value might be used.
**Cardinality:** 0..1
**Type:** [string](/string)
**Summary:** true
## CodeSystem.property.type
code | Coding | string | integer | boolean | dateTime | decimal
**Definition:** The type of the property value. Properties of type "code" contain a code defined by the code system (e.g. a reference to another defined concept).
**Cardinality:** 1..1
**Type:** [code](/code)
**Binding:** required:[concept-property-type](/valueset-concept-property-type)
**Summary:** true
## CodeSystem.concept
Concepts in the code system
**Definition:** Concepts that are in the code system. The concept definitions are inherently hierarchical, but the definitions must be consulted to determine what the meanings of the hierarchical relationships are.
**Comments:** If this is empty, it means that the code system resource does not represent the content of the code system.
**Cardinality:** 0..*
**Type:** [BackboneElement](/BackboneElement)
**Constraints:** csd-6 | error | If a concept identifies an alternate, there must be a reciprocal relationship | defineVariable('sc', code).property.all((code = 'alternateCode') implies defineVariable('ac', value).%resource.repeat(concept).where(code = %ac).exists(property.where(code = 'alternateCode').value = %sc))
## CodeSystem.concept.code
Code that identifies concept
**Definition:** A code - a text symbol - that uniquely identifies the concept within the code system.
**Conditions:** csd-1
**Cardinality:** 1..1
**Type:** [code](/code)
## CodeSystem.concept.display
Text to display to the user
**Definition:** A human readable string that is the recommended default way to present this concept to a user.
**Cardinality:** 0..1
**Type:** [string](/string)
## CodeSystem.concept.definition
Formal definition
**Definition:** The formal definition of the concept. The code system resource does not make formal definitions required, because of the prevalence of legacy systems. However, they are highly recommended, as without them there is no formal meaning associated with the concept.
**Cardinality:** 0..1
**Type:** [string](/string)
## CodeSystem.concept.designation
Additional representations for the concept
**Definition:** Additional representations for the concept - other languages, aliases, specialized purposes, used for particular purposes, etc.
**Comments:** Concepts have both a ```display``` and an array of ```designation```. The display is equivalent to a special designation with an implied ```designation.use``` of "primary designation" and a language equal to the [Resource Language](resource.html#language).
**Requirements:** Many concept definition systems support multiple representations, in multiple languages, and for multiple purposes.
**Cardinality:** 0..*
**Type:** [BackboneElement](/BackboneElement)
**Constraints:** csd-5 | error | Must have a value for concept.designation.use if concept.designation.additionalUse is present | additionalUse.exists() implies use.exists()
## CodeSystem.concept.designation.language
Human language of the designation
**Definition:** The language this designation is defined for.
**Comments:** In the absence of a language, the resource language applies.
**Cardinality:** 0..1
**Type:** [code](/code)
**Binding:** required:[all-languages](/valueset-all-languages)
## CodeSystem.concept.designation.use
Details how this designation would be used
**Definition:** A code that details how this designation would be used.
**Comments:** If no use is provided, the designation can be assumed to be suitable for general display to a human user.
**Conditions:** csd-5
**Cardinality:** 0..1
**Type:** [Coding](/Coding)
**Binding:** extensible:[designation-use](/valueset-designation-use)
## CodeSystem.concept.designation.additionalUse
Additional ways how this designation would be used
**Definition:** Additional codes that detail how this designation would be used, if there is more than one use.
**Comments:** This was added rather than increasing the cardinality of .use to 0..* in order to maintain backward compatibility.
**Conditions:** csd-5
**Cardinality:** 0..*
**Type:** [Coding](/Coding)
**Binding:** extensible:[designation-use](/valueset-designation-use)
## CodeSystem.concept.designation.value
The text value for this designation
**Definition:** The text value for this designation.
**Cardinality:** 1..1
**Type:** [string](/string)
## CodeSystem.concept.property
Property value for the concept
**Definition:** A property value for this concept.
**Cardinality:** 0..*
**Type:** [BackboneElement](/BackboneElement)
## CodeSystem.concept.property.code
Reference to CodeSystem.property.code or a FHIR defined concept-property
**Definition:** A code that is a reference to CodeSystem.property.code or is a code from [http://hl7.org/fhir/concept-properties](codesystem.html#defined-props) in the case that there is no corresponding code defined in `CodeSystem.property.code`.
**Conditions:** csd-3
**Cardinality:** 1..1
**Type:** [code](/code)
## CodeSystem.concept.property.value[x]
Value of the property for this concept
**Definition:** The value of this property.
**Cardinality:** 1..1
**Type:** [code](/code), [Coding](/Coding), [string](/string), [integer](/integer), [boolean](/boolean), [dateTime](/dateTime), [decimal](/decimal)
## CodeSystem.concept.concept
Child Concepts (is-a/contains/categorizes)
**Definition:** Defines children of a concept to produce a hierarchy of concepts. The nature of the relationships is variable (is-a/contains/categorizes) - see hierarchyMeaning.
**Cardinality:** 0..*