d
is the differential of y with respect to x. Since it is 
, when the second differential is taken, it is written as 
coming from 
.
See also exterior derivative.
- derived set
- derived unit
- Desargues, Girard
- Desargues' Theorem
- Descartes, René
- describe
- descriptive geometry
- descriptive statistics
- design methods
- destinations
- detachment, law of
- determinant
- determinantal rank
- determine
- deterministic model
- developable surface
- deviation
- devil's staircase
- df
- diagonal
- diagonal
- diagonal
- diagonal argument
- diagonal entry
- diagonalizable