QUATERNARY

I. adjective Etymology: Latin quaternarius, from quaterni four each Date: 1605 1. of, relating to, or consisting of four units or members, of, relating to, or being a number system with a base of four, of, relating to, or being the geological period from the end of the Tertiary to the present time or the corresponding system of rocks, consisting of, containing, or being an atom bonded to four other atoms, II. noun (plural -ries) Date: 1880 the Quaternary period or system of rocks, a member of a group fourth in order or rank