Definition:Combination

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Definition

Let $S$ be a set containing $n$ elements.


An $r$-combination of $S$ is a subset of $S$ which has $r$ elements.


Examples

$2$ from $3$

There are $3$ combinations of $2$ objects taken $3$ at a time:

$a \, b \quad a \, c \quad b \, c$


Also see

  • Results about combinations can be found here.


Sources