Others (like us) often use the word broadly to speak colloquially of any member of the horse family (Family Equidae). Our use of the term includes zebras, asses, and even the cat-sized, four-fingered "eohippus" that would have looked nothing like our modern domestic horses.

Because of the lack of precision of "common names," biologists have formalized the process of naming animals. Scientific names are in Latin or Latinized versions of other languages, often Greek.