Quaternary

proper noun

1. the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy

1. of, relating to, or being the Quaternary geologic period from the end of the Tertiary to the present time or the corresponding system of rocks

noun

1. term in organic chemistry used to describe degree of substitution of an atom in a molecule

adjective

1. relating to the number 4