# A quick tour of using inline variable substitution

In ModelBuilder, contents of a variable can be used as a substitute for another variable by enclosing the substituting variable in percent signs (%). Substituting variables in this manner is called **inline variable substitution**. A simple case of inline variable substitution is replacing some text or a value in a model with user input.

For examples of inline variable substitution, see the following:

Examples of inline model variable substitutionExamples of inline model environment settings variable substitutionExamples of inline system variable substitution

## Inline variable classification

Inline variables are classified into three types:

- Model variables—Any variable in a model: %variable name%.
- Environment Settings variable—Any geoprocessing environment parameter in a model: %scratchworkspace%.
- System variable—There are two system variables in ModelBuilder: %i% for a list number of a variable and %n% as the iteration number in the model.

## Rules for using inline variables

- Enclose the variable name in percent signs (%).
- Spaces within the variable name are allowed.
- Substitution is not case sensitive. Initial Value and initial value are equivalent.

## Search order for inline variables

When a model executes, the inline variables are identified and used in the following order:

- Model variables.
- Model environment settings.
- System variables (%i% and %n%).
- Variables in the parent model. If the currently running model is a submodel, the parent model's variables are searched.

9/13/2011