x_y^z is the low-level box representation for x_y^z in notebook expressions.
Timing
(Built-in Mathematica Symbol) Timing[expr] evaluates expr, and returns a list of the time in seconds used, together with the result obtained.
Trigger
(Built-in Mathematica Symbol) Trigger[Dynamic[u]] represents a trigger that can be pressed to make the dynamically updated value of u be continually increased with time from 0 to 1. Trigger[Dynamic[u], ...
Variables[poly] gives a list of all independent variables in a polynomial.
VarianceEstimatorFunction is an option for LinearModelFit and NonlinearModelFit which specifies the variance estimator to use.
VectorColorFunction is an option for VectorPlot and related functions which specifies a function to apply to determine colors of field vectors drawn.
VerifyConvergence is an option to Sum, NSum, and similar functions that specifies whether convergence checking should be done.
VertexShapeFunction is an option and property for Graph and related functions that specifies a function to use to generate primitives for rendering each vertex.
VertexSize is an option and property for Graph and related functions that specifies the size used for vertices.
$ExportFormats gives a list of export formats currently supported in your Mathematica system.