GraphicsGroup[{g_1, g_2, ...}] represents a collection of graphics objects grouped together for purposes of interactive selection in a notebook.

LengthWhile[list, crit] gives the number of continuous elements e_i starting at the beginning of list for which crit[e_i] is True.

MaxSteps is an option to functions like NDSolve that specifies the maximum number of steps to take in generating a result.

NormFunction is an option for functions such as FindFit and NDSolve which gives a function to be minimized in generating results.

ParallelNeeds["context"] evaluates Needs["context"] on all available parallel kernels.

Prolog is an option for graphics functions which gives a list of graphics primitives to be rendered before the main part of the graphics is rendered.

ReplaceList[expr, rules] attempts to transform the entire expression expr by applying a rule or list of rules in all possible ways, and returns a list of the results ...

Shortest[p] is a pattern object that matches the shortest sequence consistent with the pattern p.

StringTake["string", n] gives a string containing the first n characters in " string". StringTake["string", -n] gives the last n characters in " string". StringTake["string", ...

Functions for manipulating elements in explicit lists. This gives a list with x prepended. This inserts x so that it becomes element number 2.