Mouth
A Principal Vertex 
of a Simple Polygon 
is called a mouth if the diagonal 
is anextremal diagonal (i.e., the interior of lies in the exterior of ).
References
Toussaint, G. ``Anthropomorphic Polygons.'' Amer. Math. Monthly 122, 31-35, 1991.
- Darboux Integral
- Darboux-Stieltjes Integral
- Darboux Vector
- Darling's Products
- Dart
- Darwin-de Sitter Spheroid
- Darwin's Expansions
- Database
- Data Structure
- Daubechies Wavelet Filter
- Davenport-Schinzel Sequence
- Dawson's Integral
- Day of Week
- de Bruijn Constant
- de Bruijn Diagram
- de Bruijn Graph
- de Bruijn-Newman Constant
- de Bruijn Sequence
- de Bruijn's Theorem
- Debye Functions
- Debye's Asymptotic Representation
- Decagon
- Decagonal Number
- Decagram
- Decic Surface