Affixes

Common examples include astronomy (Greek nomos, law) and astrology (Greek logos, discourse). Astrophysics is the study of the nature of stars and other celestial bodies; an astronaut (Greek nautēs, a sailor) is a person trained to travel in a spacecraft. Some imply that a thing has points like the conventional representation of a star: an astrocyte is a star-shaped glial cell of the central nervous system; and an astroid is a hypocycloid with four cusps, shaped like a square with concave sides.