Quaternary

What does QUATERNARY mean?

1. noun

   last 2 million years

2. noun

   the cardinal number that is the sum of three and one

3. adjective

   consisting of or especially arranged in sets of four

   “quaternate leaves”

4. adjective

   coming next after the third and just before the fifth in position or time or degree or magnitude

   “the quaternary period of geologic time extends from the end of the tertiary period to the present”

Definitions from WordNet 3.1, Princeton University.