Answer: quaternary
AnswerCrossword Clue
QUATERNARYSet of four
QUATERNARYPertaining to the present period in earth history
quaternaryOf, relating to, or denoting the most recent period in the Cenozoic era, following the Tertiary period and comprising the Pleistocene and Holocene epochs (and thus including the present)
quaternaryDenoting an ammonium compound containing a cation of the form NR4+, where R represents organic groups or atoms other than hydrogen
quaternary(of a carbon atom) Bonded to four other carbon atoms
quaternaryFourth in order or rank; belonging to the fourth order
quaternarya set of four