CoefficientList[poly, var] gives a list of coefficients of powers of var in poly, starting with power 0. CoefficientList[poly, {var_1, var_2, ...}] gives an array of ...
CommonDefaultFormatTypes -> {opt_1 -> val_1, opt_2 -> val_2, ...} is an option that specifies default formats for newly created cells.
CopyDirectory["dir_1", "dir_2"] copies the directory dir_1 to dir_2.
CounterFunction is an option for counters that specifies the symbols used to display the value of the counter.
DataReversed is an option for ArrayPlot and related functions that specifies whether data should be plotted in reverse order.
DefaultFormatType is an option for cells that specifies the format used for displaying expressions in a newly created cell.
DefaultInlineFormatType is an option for cells that specifies the format used for displaying expressions in a newly created inline cell.
DeleteContents is an option for DeleteDirectory that specifies whether the contents of directories should automatically be deleted.
DelimiterFlashTime is an option for cells and notebooks that specifies how long in seconds a delimiter should flash when its matching delimiter is entered.
DiacriticalPositioning is an option for UnderscriptBox and related boxes that specifies how close diacritical characters are drawn to the base character.