---
type: "sdc-page"
title: "SDC: StructureDefinition-sdc-questionnaire-answerExpression-intro"
source: "sdc/input/pagecontent/StructureDefinition-sdc-questionnaire-answerExpression-intro.xml"
---
# SDC: StructureDefinition-sdc-questionnaire-answerExpression-intro

Additional details on the use of this extension can be found on the [Form Behavior](/sdc-behavior#answerExpression) and [Questionnaire Population](/sdc-populate#expression-based-population) pages. For details on how `answerExpression` is used to generate allowed answer options, refer to the [Expressions page - answerExpression](/sdc-expressions#answerExpression) section.