Matroid
Roughly speaking, a finite set together with a generalization of a concept from linear algebra that satisfies a natural set ofproperties for that concept. For example, the finite set could be the rows of a Matrix, and the generalizing conceptcould be linear dependence and independence of any subset of rows of the Matrix. The number of matroids with 
pointsare 1, 1, 2, 4, 9, 26, 101, 950, ... (Sloane's A002773).
References
Sloane, N. J. A. SequenceA002773/M1197in ``An On-Line Version of the Encyclopedia of Integer Sequences.''http://www.research.att.com/~njas/sequences/eisonline.html and extended entry inSloane, N. J. A. and Plouffe, S.The Encyclopedia of Integer Sequences. San Diego: Academic Press, 1995. Whitely, W. ``Matroids and Rigid Structures.'' In Matroid Applications, Encyclopedia of Mathematics and Its Applications (Ed. N. White), Vol. 40. New York: Cambridge University Press, pp. 1-53, 1992.
- Extremals
- Extreme and Mean Ratio
- Extreme Value Distribution
- Extreme Value Theorem
- Extremum
- Extremum Test
- Extrinsic Curvature
- Fabry Imbedding
- Face
- Facet
- Faceting
- Factor
- Factor Base
- Factor (Graph)
- Factor Group
- Factorial
- Factorial Moment
- Factorial Number
- Factorial Prime
- Factorial Sum
- Factoring
- Factorion
- Factorization
- Factor Level
- Factor Ring