> ## 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.

# Age

> Base StructureDefinition for Age Type: A duration of time during which an organism (or a process) has existed.

## 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 |
| value      | No       | decimal                                                | Numerical value (with implicit precision)     |
| comparator | No       | code                                                   | how to understand the value                   |
| unit       | No       | string                                                 | Unit representation                           |
| system     | No       | uri                                                    | System that defines coded unit form           |
| code       | No       | code                                                   | Coded form of the unit                        |