[ trahy-mes-ter, trahy-mes- ]
/ traɪˈmɛs tər, ˈtraɪ mɛs- /


a term or period of three months.
one of the three approximately equal terms into which the year is divided by some colleges, schools, etc.

Nearby words

  1. trimble,
  2. trime,
  3. trimer,
  4. trimeric,
  5. trimerous,
  6. trimestral,
  7. trimetallic,
  8. trimeter,
  9. trimethadione,
  10. trimethoprim

Origin of trimester

1815–25; < French trimestre < Latin trimē(n)stris of three months, equivalent to tri- tri- + -mē(n)stris (see semester)

Related formstri·mes·tral [trahy-mes-truh l] /traɪˈmɛs trəl/, tri·mes·tri·al, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for trimester

British Dictionary definitions for trimester


/ (traɪˈmɛstə) /


a period of three months
(in some US and Canadian universities or schools) any of the three academic sessions
Derived Formstrimestral or trimestrial, adjective

Word Origin for trimester

C19: from French trimestre, from Latin trimēstris of three months, from tri- + mēnsis month

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 trimester



1821, "period of three months," from French trimestre (early 17c.), from Latin trimestris "of three months," from tri- "three" (see tri-) + mensis "month" (see moon (n.)). Specific obstetrics sense is attested from 1916.

Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for trimester


[ trī-mĕstər, trīmĕs′- ]


A period of three months.

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.