[ tur-shee-er-ee, tur-shuh-ree ]
/ ˈtɜr ʃiˌɛr i, ˈtɜr ʃə ri /
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noun, plural ter·ti·ar·ies.



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Origin of tertiary

1540–50; <Latin tertiārius of third part or rank, equivalent to terti(us) third + -ārius-ary


post-Ter·ti·ar·y, adjectivepre-Ter·ti·ar·y, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2021

Example sentences from the Web for tertiary

British Dictionary definitions for tertiary (1 of 2)

/ (ˈtɜːʃərɪ) /


noun plural -tiaries

Also called: tertial ornithol rare any of the tertiary feathers
RC Church a member of a Third Order

Word Origin for tertiary

C16: from Latin tertiārius containing one third, from tertius third

British Dictionary definitions for tertiary (2 of 2)

/ (ˈtɜːʃərɪ) /


of, denoting, or formed in the first period of the Cenozoic era, which lasted for 63 million years, during which mammals became dominant


the Tertiary the Tertiary period or rock system, divided into Palaeocene, Eocene, Oligocene, Miocene, and Pliocene epochs or series
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for tertiary

[ tûrshē-ĕr′ē ]


Third in place, order, degree, or rank.
Of or relating to salts of acids containing three replaceable hydrogen atoms.
Of or relating to organic compounds in which a group is bound to three nonelementary radicals.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Scientific definitions for tertiary

[ tûrshē-ĕr′ē ]


Tertiary. The first period of the Cenozoic Era, from about 65 to 2 million years ago. During this time the continents took on their present form, and the climate changed from being warmer and wetter, in the early part of the period, to being drier and cooler in the later part. Mammals replaced dinosaurs as the dominant form of terrestrial animal life, and many modern types of flowering plants, insects, mollusks, fish, amphibians, reptiles, and birds appeared. The Tertiary is subdivided into the Paleogene and the Neogene, although these terms are not as widely used as are the names of the epochs that constitute them. See Chart at geologic time.


  1. Relating to or having a carbon atom that is attached to three other carbon atoms in a molecule.
  2. Relating to an organic molecule, such as an alcohol, in which the functional group is attached to a tertiary carbon.
Relating to an advanced level of medical care, usually provided by subspecialists after the delivery of primary medical care. Compare primary secondary.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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