what is the plural of genius?
In most cases, one can acceptably use geniuses as the plural. In fact, when referring to the quality of genius (as opposed to an individual possessing certain qualities or a certain nature), geniuses is the plural that one should normally use. However, when referring to an individual as a genius, the most correct plural is genii (that's three syllables). This is because genius is derived from Latin. It is the first-person masculine singular form of the word. The first-person masculine plural is genii.
In ancient Rome, the genius (plural in Latin genii) was the guiding spirit or tutelary deity of a person, family (gens), or place (genius loci). The noun is related to the Latin verb genui, genitus, to bring into being, create, produce, as well as to the Greek word for birth.