Covariance[v_1, v_2] gives the covariance between the vectors v_1 and v_2.Covariance[m] gives the covariance matrix for the matrix m.Covariance[m_1, m_2] gives the covariance ...

CreateDialog[expr] creates a dialog notebook containing expr and opens it in the front end.CreateDialog[expr, obj] replaces the notebook represented by the notebook object ...

DefaultNaturalLanguage is an option for character selections that specifies the language used when checking the spelling of a word in a human natural language selection.

Deletable is an option for Cell that specifies whether the cell can be deleted interactively using the front end.

DelimiterMatching is an option for selections that specifies whether an opening delimiter will match only its respective closing delimiter or any closing delimiter.

DialogSymbols is an option for Dialog which gives a list of symbols whose values should be localized in the dialog.

DifferentialD[x] displays as \[DifferentialD]x.

DigitQ[string] yields True if all the characters in the string are digits in the range 0 through 9, and yields False otherwise.

DisplayAllSteps is an option to Animate and related functions that specifies whether all frames should be displayed in an animation, even if to do so would slow the animation ...

DisplayEndPacket[] is a MathLink packet that indicates the end of a series of expressions relating to a postscript graphic.