CellLabel is an option for Cell which gives the label to use for a particular cell.
CellTags is an option for Cell that gives a list of tags to associate with a cell.
ChartBaseStyle is an option for charting functions that specifies the base style for all chart elements.
CheckAbort[expr, failexpr] evaluates expr, returning failexpr if an abort occurs.
CirclePlus[x, y, ...] displays as x\[CirclePlus]y\[CirclePlus]....
ClearSystemCache[] clears internal system caches of stored results.
C
(Built-in Mathematica Symbol) C[i] is the default form for the i\[Null]\[Null]^th parameter or constant generated in representing the results of various symbolic computations.
ColorFunctionScaling is an option for graphics functions that specifies whether arguments supplied to a color function should be scaled to lie between 0 and 1.
ColorQuantize[image, n] gives an approximation to image that uses only n distinct colors.
ColumnAlignments is an option for the low-level function GridBox that specifies how entries in each column should be aligned.