DownRightTeeVector[x, y, ...] displays as x \[DownRightTeeVector] y \[DownRightTeeVector] ....
DownRightVectorBar[x, y, ...] displays as x\[DownRightVectorBar]y\[DownRightVectorBar]....
DownRightVector[x, y, ...] displays as x \[DownRightVector] y \[DownRightVector] ....
DownTeeArrow[x, y, ...] displays as x\[DownTeeArrow]y\[DownTeeArrow]....
DownValues[f] gives a list of transformation rules corresponding to all downvalues defined for the symbol f.
DragAndDrop is a global front end option that specifies whether to allow drag-and-drop editing.
Drop
(Built-in Mathematica Symbol) Drop[list, n] gives list with its first n elements dropped. Drop[list, -n] gives list with its last n elements dropped. Drop[list, {n}] gives list with its n\[Null]^th ...
DSolve
(Built-in Mathematica Symbol) DSolve[eqn, y, x] solves a differential equation for the function y, with independent variable x. DSolve[{eqn_1, eqn_2, ...}, {y_1, y_2, ...}, x] solves a list of ...
Dt
(Built-in Mathematica Symbol) Dt[f, x] gives the total derivative d f/d x. Dt[f] gives the total differential d f. Dt[f, {x, n}] gives the multiple derivative d^n f/d x^n. Dt[f, x_1, x_2, ...] gives d/d ...
DualSystemsModel[ss] gives the dual of the StateSpaceModel object ss.