[tur-shee-er-ee, tur-shuh-ree]


noun, plural ter·ti·ar·ies.

Origin of tertiary

1540–50; < Latin tertiārius of third part or rank, equivalent to terti(us) third + -ārius -ary
Related formspost-Ter·ti·ar·y, adjectivepre-Ter·ti·ar·y, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Related Words for tertiary

triennial, tertian

Examples from the Web for tertiary

Contemporary Examples of tertiary

Historical Examples of tertiary

British Dictionary definitions for tertiary



third in degree, order, etc
(of education) taking place after secondary school, such as at university, college, etc
(of an industry) involving services as opposed to extraction or manufacture, such as transport, finance, etcCompare primary (def. 8b), secondary (def. 7)
RC Church of or relating to a Third Order
  1. (of an organic compound) having a functional group attached to a carbon atom that is attached to three other groups
  2. (of an amine) having three organic groups attached to a nitrogen atom
  3. (of a salt) derived from a tribasic acid by replacement of all its acidic hydrogen atoms with metal atoms or electropositive groups
Also called: tertial ornithol rare of, relating to, or designating any of the small flight feathers attached to the part of the humerus nearest to the body

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



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

Word Origin and History for tertiary

1650s, "of the third order, rank, degree, etc.," from Latin tertiarius "of or pertaining to a third," from tertius "third, a third," from root of tres "three" (see three). The geological sense (with capital T-) of "era after the Mesozoic" (which formerly was called the Secondary) is attested from 1794, after Italian terziari, used in this sense 1760 by Italian geologist Giovanni Arduino (1714-1795).

Online Etymology Dictionary, © 2010 Douglas Harper

tertiary in Medicine




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.

tertiary in Science




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.