> ## Documentation Index
> Fetch the complete documentation index at: https://docs.metriport.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Population

> Base StructureDefinition for Population Type: A populatioof people with some set of grouping criteria.

## Properties

| Name                   | Required | Type                                                                                                         | Description                                                                            |
| ---------------------- | -------- | ------------------------------------------------------------------------------------------------------------ | -------------------------------------------------------------------------------------- |
| id                     | No       | string                                                                                                       | Unique id for inter-element referencing                                                |
| extension              | No       | [Extension](/medical-api/fhir/data-types/extension)\[]                                                       | Additional content defined by implementations                                          |
| modifierExtension      | No       | [Extension](/medical-api/fhir/data-types/extension)\[]                                                       | Extensions that cannot be ignored even if unrecognized                                 |
| age\[x]                | No       | [Range](/medical-api/fhir/data-types/range), [CodeableConcept](/medical-api/fhir/data-types/codeableconcept) | The age of the specific population                                                     |
| gender                 | No       | [CodeableConcept](/medical-api/fhir/data-types/codeableconcept)                                              | The gender of the specific population                                                  |
| race                   | No       | [CodeableConcept](/medical-api/fhir/data-types/codeableconcept)                                              | Race of the specific population                                                        |
| physiologicalCondition | No       | [CodeableConcept](/medical-api/fhir/data-types/codeableconcept)                                              | The existing physiological conditions of the specific population to which this applies |