A collateral adjective is an adjective whose word origin is different from the noun it represents. English has many collateral adjectives from French, Latin, and Greek, because many English words come from these languages. For example, the adjectives for the native English words "horse" and "moon" are "equine" and "lunar". Equine comes from the Latin "equus". Lunar comes from the Latin "luna". This is why the study of horses is called "equine science" and the calendar for the moon called the "lunar calendar".