quaternary

(kwät′ər ner′ē, kwə tʉr′nə rē)

adjective

consisting of four; in sets of four
designating or of the second and current geologic period of the Cenozoic Era, usually subdivided into the Pleistocene and Holocene epochs and characterized by a series of ice ages, the first toolmaking cultures, and the rise of modern human culture
Chem.
1. designating a compound or alloy containing four different components or elements: quaternary silver
2. being, of, or containing an atom linked to four carbon atoms: a quaternary nitrogen atom

Origin: L quaternarius < quaterni, four together, four each < quater, four times < base of quattuor, four

See quaternary in American Heritage Dictionary 4

adjective

Consisting of four; in fours.
Quaternary Of or belonging to the geologic time, system of rocks, or sedimentary deposits of the second period of the Cenozoic Era, from the end of the Tertiary Period through the present, characterized by the appearance and development of humans and including the Pleistocene and Holocene epochs. See Table at geologic time.
Chemistry Relating to an atom bonded to four carbon atoms: a quarternary nitrogen atom.

noun pl. qua·ter·nar·ies