Edit FitNesse.UserGuide.MarkupVariables:

!2 Defining and Expressing Variables.
You can define a variable to represent any amount of text.  The text in a variable is never interpreted as wiki markup.  It is always raw literal text.
 * Variable names may contain letters, numbers, and periods; e.g., MYTEST.someVar or user.name
 * You can define a variable in any of these three ways: 
  * !style_code(!-!define var {text}-!)
  * !style_code[!-!define var (text)-!]
  * !style_code(!-!define var [text]-!)
   * The reason there are three forms is so that you can include braces, brackets, or parenthesis in your variables.
 * The variable text can span many lines as shown below:
{{{
!define myVariable {
This is the
text of my
variable
}  }}}
!define myVariable {
this is the
text of my
variable
}
You express the value of a variable like this: !-${myVariable}-!.  This expression is replaced with the value of the variable.

''The value of the variable is: ${myVariable}.''

If a variable is expressed on a page, but is not found, then its parent pages are searched in order.
If the variable is not found in any ancestor pages, FitNesse will inspect System.properties.

There are several [[pre-defined variables][<UserGuide.QuickReferenceGuide#VARIABLES]] that you can use on your pages.

See [[Variable fitnesse test][.FitNesse.SuiteAcceptanceTests.SuiteWidgetTests.TestVariables]], [[Parent Variable fitnesse test][.FitNesse.SuiteAcceptanceTests.SuiteWidgetTests.TestParentVariables]] and [[Define Variables in System Properties test][.FitNesse.SuiteAcceptanceTests.SuiteWidgetTests.TestVariablesFromSystemProperties]]

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