# Definitions

This chapter introduces the tools for creating and editing mathematical models by giving each variable a formula that defines how to compute its value in its * definition*. The definition of a variable can be a simple number, text, a probability distribution, or a more complicated expression. It can also be a list or table of numbers or other expressions. Subsequent chapters present more details about using mathematical expressions, arrays, and probability distributions.

## Sections

- Creating or editing a definition
- The Expression popup menu
- Expression Assist
- Object Finder dialog
- Definition menu
- The domain of possible values
- Check attribute
- Syntax coloring and fonts and error_underlining

## See Also

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