ByteOrdering is an option for BinaryRead, BinaryWrite, and related functions that specifies what ordering of bytes should be assumed for your computer system.
CellBaseline is an option for Cell which specifies where the baseline of the cell should be assumed to be when it appears inside another cell.
CellBracketOptions -> {opt_1 -> val_1, opt_2 -> val_2, ...} is an option for cells that specifies settings for cell brackets.
CellLabel is an option for Cell which gives the label to use for a particular cell.
CheckAbort[expr, failexpr] evaluates expr, returning failexpr if an abort occurs.
Checkbox[x] represents a checkbox with setting x, displayed as CheckboxBox[True] when x is True and CheckboxBox[False] when x is False. Checkbox[Dynamic[x]] takes the setting ...
CirclePlus[x, y, ...] displays as x\[CirclePlus]y\[CirclePlus]....
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.
ColumnAlignments is an option for the low-level function GridBox that specifies how entries in each column should be aligned.