Ternary

Ternary (also known as Trinary or base 3) is a positional number system structured around the number 3 and its powers. It is the second prime base and the second lowest standard base.

Usage
Ternary, while much less useful than binary, is still very useful. It has been used most notably in measurement units. The Cantor set can be defined with the help of ternary numbers as "all points in [0, 1] that can be represented in ternary with no 1s". In general, anything that can have three possible states is ternary. For example, if we define a finger as having the three possible states of "open" (2), "closed" (0) and "half-open" (1), then we can count up to 310-1 on our fingers using the binary finger counting method.

Fractions
As ternary is a prime base, a ternary fraction will only terminate if the denominator is a power of 3.

Related number systems

 * Balanced ternary is a highly useful balanced base corresponding to ternary.
 * Negaternary is the negative base corresponding to ternary.
 * Bijective ternary is the bijective base corresponding to ternary.
 * Nonary digits correspond to 2 ternary digits.
 * Heptavigesimal digits correspond to 3 ternary digits.
 * Unoctogesimal digits correspond to 4 ternary digits.