ColorRules is an option for ArrayPlot which specifies how colors of cells should be determined from values.
CompiledFunction[args...] represents compiled code for evaluating a compiled function.
ComplexityFunction is an option for Simplify and other functions which gives a function to rank the complexity of different forms of an expression.
patt /; test is a pattern which matches only if the evaluation of test yields True. lhs :> rhs /; test represents a rule which applies only if the evaluation of test yields ...
Contours is an option for contour plots that specifies the contours to draw.
ControllerPath is an option that gives a list of external controllers or classes of controllers to try for functions such as ControllerState, Manipulate, and Graphics3D.
ControlPlacement is an option for Manipulate, TabView, and other control objects that specifies where controls should be placed.
DateTicksFormat is an option for DateListPlot which specifies how date tick labels should be formatted.
DialogInput[expr] interactively puts up expr as a dialog notebook, waits until a DialogReturn[e] is evaluated from within it, and then returns the result e. DialogInput[{x = ...
DigitBlock is an option for NumberForm and related functions that specifies the maximum length of blocks of digits between breaks.