Normal Subgroup
Let 
be a Subgroup of a Group 
. Then is a normal subgroup of , written 
, if
for every element
in . Normal subgroups are also known as Invariant Subgroups.See also Group, Subgroup- 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
- Decidable
- Decillion
- Decimal