ac·​a·​rus ˈa-kə-rəs How to pronounce acarus (audio)
plural acari ˈa-kə-ˌrī How to pronounce acarus (audio)
: mite
especially : one of a formerly extensive genus (Acarus)

Word History


borrowed from New Latin, a re-formation as a masculine noun of Greek akarí (neuter) "mite," probably of pre-Greek substratal origin

Note: The masculine re-formation of Greek akarí is perhaps late Medieval Latin; the form appears in 16th-century Latin/vernacular dictionaries such as the Dutch-Latin dictionary of Cornelis Kiliaan. Greek akarí is conventionally associated with the adjective akarḗs, "tiny, minute," though of equal if not more relevance might be kárnos, "louse" (Hesychius) and kóris, "bedbug."

First Known Use

1657, in the meaning defined above

Time Traveler
The first known use of acarus was in 1657

Dictionary Entries Near acarus

Cite this Entry

“Acarus.” Dictionary, Merriam-Webster, Accessed 29 May. 2023.

Medical Definition


ac·​a·​rus ˈak-ə-rəs How to pronounce acarus (audio)
capitalized : a genus of arachnids including a number of small mites and formerly including all mites and ticks
plural acari -ˌrī How to pronounce acarus (audio) -ˌrē How to pronounce acarus (audio) : mite
especially : one of the genus Acarus or formerly included in this genus
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