ternary

adjective

1. made up of three parts or things; threefold; triple
2. third in order or rank
3. Chem. of or containing three different atoms, elements, radicals, etc.
4. Math.
   1. having three as a base
   2. involving three variables
5. Metallurgy of an alloy of three elements

Origin: ME < L ternarius < terni, three each < tres, three

noun pl. ternaries