leaver / lever are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
leaver: NA
lever: (noun) a rigid bar pivoted about a fulcrum. (noun) a simple machine that gives a mechanical advantage when given a fulcrum. (noun) a flat metal tumbler in a lever lock.
leaver: l·IY·v·er
lever: l·EH·v·er
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)