The ternary numeral system (also called base 3) has three as its base. Analogous to a bit, a ternary digit is a trit (trinary digit). One trit is equivalent to log₂3 (about 1.58496) bits of information.

Although ternary most often refers to a system in which the three digits 0, 1, and 2 are all non-negative numbers, the adjective also lends its name to the balanced ternary system, used in comparison logic and ternary computers.