[kwəˈtəːn(ə)ri], (Adjective)

Definitions:
- fourth in order or rank; belonging to the fourth order

- relating to or denoting the most recent period in the Cenozoic era, following the Tertiary period and comprising the Pleistocene and Holocene epochs

- denoting an ammonium compound containing a cation of the form NR₄ ⁺, where R represents organic groups or atoms other than hydrogen


Phrases:

Origin:
late Middle English (as a noun denoting a set of four): from Latin quaternarius, from quaterni ‘four at once’, from quater ‘four times’, from quattuor ‘four’

[kwəˈtəːn(ə)ri], (Noun)

Definitions:
- the Quaternary period or the system of deposits laid down during it


Phrases:

Origin:
late Middle English (as a noun denoting a set of four): from Latin quaternarius, from quaterni ‘four at once’, from quater ‘four times’, from quattuor ‘four’