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1835 (as an adjective 1833), from Modern Latin Rodentia, the order name, from Latin rodentem (nominative rodens), present participle of rodere "to gnaw, eat away," from PIE root *red- "to scrape, scratch, gnaw" (cf. Sanskrit radati "scrapes, gnaws," radanah "tooth;" Latin radere "to scrape;" Welsh rhathu "scrape, polish"). Uncertain connection to Old English rætt (see rat (n.)).
Any of various very numerous, mostly small mammals of the order Rodentia, having large front teeth used for gnawing. The teeth grow throughout the animal's life, and are kept from getting too long by gnawing. Rodents make up about half the living species of mammals, and include rats, mice, beavers, squirrels, lemmings, shrews, and hamsters.