quaternary

UK: 'quaternary', 'Quaternary': /kwəˈtɜːnərɪ/

US: (kwot′ər ner′ē, kwə tûr′nə rē)

Inflections of 'quaternary' (n): npl: quaternaries

WordReference Random House Unabridged Dictionary of American English © 2025

quat•er•nar•y  (kwot′ər ner′ē, kwə tûr′nə rē), adj., n., pl. -nar•ies. 
adj. 

1. consisting of four.
2. arranged in fours.
3. Geology (cap.) noting or pertaining to the present period of earth history, forming the latter part of the Cenozoic Era, originating about 2 million years ago and including the Recent and Pleistocene Epochs. See table under geologic time. 
4. Metallurgy (of an alloy) having four principal constituents.

n. 

5. a group of four.
6. the number four.
7. Geology (cap.) the Quaternary Period or System.

• Latin quaternārius consisting of four, equivalent. to quatern(ī) four at a time + -ārius -ary
• late Middle English 1400–50

Collins Concise English Dictionary © HarperCollins Publishers::

quaternary / kwəˈtɜːnərɪ/ adjective

1. consisting of fours or by fours
2. fourth in a series
3. containing or being an atom bound to four other atoms or groups

noun ( -naries)

1. the number four or a set of four

Etymology: 15th Century: from Latin quaternārius each containing four, from quaternī by fours, distributive of quattuor four

Collins Concise English Dictionary © HarperCollins Publishers::

Quaternary / kwəˈtɜːnərɪ/ adjective

1. of, denoting, or formed in the most recent period of geological time, which succeeded the Tertiary period nearly two million years ago

noun

1. the Quaternary ⇒ the Quaternary period or rock system, divided into Pleistocene and Holocene (Recent) epochs or series