DocumentationMathematicaBuilt-in FunctionsNew in Version 5.0Algebraic Computation
$Assumptions is the default setting for the Assumptions option used in such functions as Simplify, Refine and Integrate.
The value of $Assumptions can be modified using Assuming.
The initial setting for $Assumptions is True.
See Section 3.3.10.
See also: Assuming, Block.
New in Version 5.0.