Cardinal Number
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Definition
Cardinal Number

Supplementary definitions
Cardinal number 

In mathematics, cardinal numbers, or cardinals for short, are generalized numbers used to measure the cardinality (size) of sets. For finite sets, the cardinality is given by a natural number, which is simply the number of elements in the set. There are also transfinite cardinal numbers that describe the sizes of infinite sets. This extract is licensed under the Creative Commons AttributionShareAlike license. It uses material from the article "Cardinal number", retrieved 1 Jan 2009. 
Examples
 The cardinal number of the set [math]A=\left \{2, 4, 9, 7, 1, 8\right\}\,[/math] is [math]6\,[/math].
Tip: Count the number of items in the set [math]A[/math] above
 The cardinal number of the set [math]G=\left \{\alpha, \beta, \gamma, \delta, \epsilon, \zeta, \eta, \theta, \iota, \kappa, \lambda, \mu, \nu, \xi, \mathit{o}, \pi, \rho, \sigma, \tau, \upsilon, \phi, \chi, \psi, \omega \right\}\,[/math] is [math]24\,[/math].
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