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# Defining Your Own Functions

Smoke allows you to define your own functions and use them like any other predefined function. By defining functions in terms of existing functions, you can simplify the creation of complex expressions in your animations.

NoteYou should have a good understanding of how to use functions in expressions before you define your own functions.

#### Topics in this section

- The Functions File
- Defining a Function
- Comments
- Sample Function Definitions