Pattern matching makes possible some of the most succinct and elegant programs in the Mathematica language—immediately compressing large numbers of conditional cases into simple, readable and efficient pattern specifications.
Cases — a list of elements matching a pattern
Position — positions of elements matching a pattern
Count — a count of occurrences of a pattern
DeleteCases — delete all occurrences of a pattern
MemberQ — test if any member of a list matches a pattern
FreeQ — test if an expression is free of a pattern
MatchQ — test whether an expression matches a pattern