Rest has several different meanings. See:

• rest (music), a pause in a piece of music.
• rest (object), a support for a musket or billiards or snooker cue.
• rest (physics), the relation between two observers.
• rest as action, to relax, see recreation.
• The reserves of the Bank of England.
• In software engineering, REST is an acronym for Representational State Transfer.
• In chemistry a rest (abbreviated R) is a variable part of a molecule attached to a given core structure. See: Functional group and side chain.