leaches / leeches 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. 👇
leaches: (noun) the process of leaching. (verb) cause (a liquid) to leach or percolate. (verb) permeate or penetrate gradually. (verb) remove substances from by a percolating liquid.
leeches: (noun) carnivorous or bloodsucking aquatic or terrestrial worms typically having a sucker at each end. (noun) a follower who hangs around a host (without benefit to the host) in hope of gain or advantage.
leaches: l·IY·ch·ih·z
leeches: l·IY·ch·ih·z
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)