> For the complete documentation index, see [llms.txt](https://docs.snomed.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.snomed.org/snomed-ct-specifications/snomed-ct-editorial-guide/readme/authoring/domain-specific-modeling/substance/substance-defining-attributes.md).

# Substance Defining Attributes

The following defining attributes correspond to the *Substance Attribute Summary* table.

## Has disposition

This attribute enables the creation of an association between a substance concept and a disposition. A disposition is defined as a behavior that a substance will exhibit or participate in, given the appropriate context.

## Is modification of

This attribute indicates that the concept is a structural modification of another concept, and that the substance's intrinsic physicochemical properties remain unchanged.

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