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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 leisure; compare recreation.

Bank reserves, in the terminology of the Bank of England

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

Representational State Transfer, in software engineering an architectural principle for designing web services, abbreviated REST

reStructuredText, a markup language abbreviated ReST or reST