Subset
A portion of a Set. 
is a subset of 
(written 
) Iff every member of is a member of. If is a Proper Subset of (i.e., a subset other than the set itself), this is written 
.
A Set of 
elements has 
subsets (including the set itself and the Empty Set). For sets of 
, 2,... elements, the numbers of subsets are therefore 2, 4, 8, 16, 32, 64, ... (Sloane's A000079). For example,the set 
has the two subsets 
and . Similarly, the set 
has subsets (the Empty Set, , 
, and .
References
Courant, R. and Robbins, H. What is Mathematics?: An Elementary Approach to Ideas and Methods, 2nd ed. Oxford, England: Oxford University Press, p. 109, 1996. Ruskey, F. ``Information of Subsets of a Set.'' http://sue.csc.uvic.ca/~cos/inf/comb/SubsetInfo.html. Sloane, N. J. A. SequenceA000079/M1129in ``An On-Line Version of the Encyclopedia of Integer Sequences.''http://www.research.att.com/~njas/sequences/eisonline.html and Sloane, N. J. A. and Plouffe, S.The Encyclopedia of Integer Sequences. San Diego: Academic Press, 1995.
- Peano Arithmetic
- Peano Curve
- Peano-Gosper Curve
- Peano's Axioms
- Peano Surface
- Pear Curve
- Pearls of Sluze
- Pear-Shaped Curve
- Pearson-Cunningham Function
- Pearson Kurtosis
- Pearson Mode Skewness
- Pearson's Correlation
- Pearson's Function
- Pearson Skewness
- Pearson's Skewness Coefficients
- Pearson System
- Pearson Type III Distribution
- Peaucellier Cell
- Peaucellier Inversor
- Peaucellier's Linkage
- Pedal
- Pedal Circle
- Pedal Coordinates
- Pedal Curve
- Pedal Line