base 7 is a positional numeral system with seven as its base. It uses 7 different digits for representing numbers. The digits for base 7 could be 0, 1, 2, 3, 4, 5, and 6.
ternary (base 3)
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.