Sign
(Built-in Mathematica Symbol) Sign[x] gives -1, 0, or 1 depending on whether x is negative, zero, or positive.
CompleteGraph[n] gives the complete graph with n vertices K_n.CompleteGraph[{n_1, n_2, ..., n_k}] gives the complete k-partite graph with n_1 + n_2 + \[CenterEllipsis] + n_k ...
ArgColor, ArgShade and ColorCircle are obsolete, with simple definitions in terms of system functions.
AbortProtect[expr] evaluates expr, saving any aborts until the evaluation is complete.
BetweennessCentrality[g] gives a list of betweenness centralities for the vertices in the graph g.
CriticalSection[{var_1, var_2, ...}, expr] locks the variables var_i with respect to parallel computation, evaluates expr, then releases the var_i.
DateFunction is an option for DateListPlot that specifies how dates given as input should be converted to date lists.
FlattenAt[list, n] flattens out a sublist that appears as the n\[Null] th element of list. If n is negative, the position is counted from the end. FlattenAt[expr, {i, j, ...
InputForm[expr] prints as a version of expr suitable for input to Mathematica.
MedianDeviation[list] gives the median absolute deviation from the median of the elements in list.