The basic meaning of the suffix -oid is “like” or “resembling.” Words ending in -oid are generally adjectives but can also be nouns. Thus humanoid means “having human characteristics or form” (adjective sense) or “a being having human form” (noun sense). Nouns ending in -oid form adjectives by adding the suffix -al: spheroid, spheroidal; trapezoid, trapezoidal. The suffix -oid comes from the Greek suffix -oeides, from eidos, meaning “shape, form.”
