Commutator
Let 
, 
, ...be Operators. Then the commutator of and isdefined as
 | (1) |
, 
, ...be constants. Identities include |  |  | (2) |
 | | | (3) |
 | |  | (4) |
 | |  | (5) |
 | |  | (6) |
 | | | (7) |
 | |  | |
| (8) |
The commutator can be interpreted as the ``infinitesimal'' of the commutator of a Lie Group.
Let 
and 
be Tensors. Then
 | (9) |
- Elliptic Umbilic Catastrophe
- Ellison-Mendès-France Constant
- Elongated Cupola
- Elongated Dipyramid
- Elongated Dodecahedron
- Elongated Gyrobicupola
- Elongated Gyrocupolarotunda
- Elongated Orthobicupola
- Elongated Orthobirotunda
- Elongated Orthocupolarotunda
- Elongated Pentagonal Cupola
- Elongated Pentagonal Dipyramid
- Elongated Pentagonal Gyrobicupola
- Elongated Pentagonal Gyrobirotunda
- Elongated Pentagonal Gyrocupolarotunda
- Elongated Pentagonal Orthobicupola
- Elongated Pentagonal Orthobirotunda
- Elongated Pentagonal Orthocupolarotunda
- Elongated Pentagonal Pyramid
- Elongated Pentagonal Rotunda
- Elongated Pyramid
- Elongated Rotunda
- Elongated Square Cupola
- Elongated Square Dipyramid
- Elongated Square Gyrobicupola