# Definition:Combination

## 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.