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.
For the most part we are talking about the Mongolian Gerbil which is the species of Gerbil that most people have as a pet. 1. Gerbils are mammals and are from the same family of animals as rats, mice, guinea pigs and hamsters, which is the rodent family.