Compiled is an option for various numerical and plotting functions which specifies whether the expressions they work with should automatically be compiled.
ControlsRendering is a Style option that specifies how controls should be rendered.
DateFunction is an option for DateListPlot that specifies how dates given as input should be converted to date lists.
DelimiterFlashTime is an option for cells and notebooks that specifies how long in seconds a delimiter should flash when its matching delimiter is entered.
DifferenceRootReduce[expr, n] attempts to reduce expr to a single DifferenceRoot object as a function of n.
Direction is an option for Limit that specifies the direction in which the limit is taken.
Directive[g_1, g_2, ...] represents a single graphics directive composed of the directives g_1, g_2, ....
DirectoryName["name"] extracts the directory name from the specification for a file.
DotDashed is a graphics directive specifying that lines that follow should be drawn dot-dashed.
Dotted
(Built-in Mathematica Symbol) Dotted is a graphics directive specifying that lines that follow should be drawn dotted.