Word Origin and History for semi-Expand before vowels sem-, word-forming element meaning half, part, partly; partial, imperfect; twice, from Latin semi-half, from PIE *semi-half (cf. Sanskrit sami half, Greek hemi-half, Old English sam-, Gothic sami-half).
Well-known rodents include mice, rats, squirrels, prairie dogs, porcupines, beavers, guinea pigs, hamsters, gerbils and capybaras. Other animals such as rabbits, hares, and pikas, whose incisors also grow continually, were once included with them, but are now considered to be in a separate order, the Lagomorpha.
In our phylum chordata, the mammals, birds, reptiles, amphibians, and bony fish are in five different CLASSES. There are some other classes too - mostly weird fish. Below the class is the order. In our class mammalia, the cows, rabbits, whales, cats, armadillos, elephants, and people are in 7 different ORDERS.