Mutual exclusivity
Appearance
Events E1, E2, ... , En are said to be mutually exclusive if the occurrence of any one them automatically implies the non-occurrence of the remaining n-1 events.
Examples:
A flipped coin coming up heads and the same coin coming up tails are mutually exclusive events.
A student passing a test and failing it are also mutually exclusive.
(By Gerami F. Havewala)