DeletionWarning is an option for InterpretationBox or TagBox objects that specifies whether a warning is issued if the box is deleted.
Del
(Built-in Mathematica Symbol) Del[x] displays as \[Del]x.
Diamond
(Built-in Mathematica Symbol) Diamond[x, y, ...] displays as x\[Diamond]y\[Diamond]....
DotEqual[x, y, ...] displays as x \[DotEqual] y \[DotEqual] ....
DoubleDownArrow[x, y, ...] displays as x\[DoubleDownArrow]y....
DoubleLongLeftArrow[x, y, ...] displays as x\[DoubleLongLeftArrow]y\[DoubleLongLeftArrow]....
DoubleLongLeftRightArrow[x, y, ...] displays as x\[DoubleLongLeftRightArrow]y\[DoubleLongLeftRightArrow]....
DoubleLongRightArrow[x, y, ...] displays as x\[DoubleLongRightArrow]y\[DoubleLongRightArrow]....
DoubleRightArrow[x, y, ...] displays as x \[DoubleRightArrow] y \[DoubleRightArrow] ....
DoubleUpArrow[x, y, ...] displays as x\[DoubleUpArrow]y\[DoubleUpArrow]....