MathGloss

If there are aa ways of doing one thing and bb ways of doing another thing, then there are abab ways of doing both things. This can be extended inductively.

Set theoretically, this is the definition of the product of cardinal numbers: S1S2Sn=S1×S2×Sn\vert S_1\vert \cdot\vert S_2\vert \cdots\vert S_n\vert = \vert S_1\times S_2\times\cdots S_n\vert where \vert \cdot\vert is the cardinal number of the sets SiS_i and ×\times is the Cartesian product of sets. The sets need not be finite nor does the number of sets.

Wikidata ID: Q557624