tri·​mes·​ter | \ (ˌ)trī-ˈme-stər How to pronounce trimester (audio) , ˈtrī-ˌ\

Definition of trimester

1 : a period of three or about three months especially : any of three periods of approximately three months each into which a human pregnancy is divided
2 : one of three terms into which the academic year is sometimes divided

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Did You Know?

Semester, which comes from the Latin words for "six" and "month", has come to mean half an academic year when the year is divided into two segments. When an academic year is divided into three segments, each is called a trimester (which is usually a bit more accurate, since each segment often is close to three months in length). Some colleges operate on the "quarter" system, with the summer being the fourth quarter, but this just means that each quarter is basically a trimester. In a human pregnancy, a trimester is three months long, representing one-third of the nine months that a typical pregnancy lasts.

Examples of trimester in a Sentence

development in the first trimester

Recent Examples on the Web

An official date for Valencia’s testimonial is yet to be set, but Paz said it will be played within the first trimester of the 2020 campaign., "Manchester United to Give Departed Captain Antonio Valencia a Testimonial Match Next Season," 2 July 2019 And about 90 percent of the abortions in 2018 were performed during the first trimester. Ryan Faircloth, Twin Cities, "Abortions in Minnesota decreased last year, according to new state report," 1 July 2019 The Supreme Court won't revive Alabama's ban on the most commonly used procedure in second-trimester abortions. CBS News, "Justices won't revive Alabama ban on abortion procedure," 28 June 2019 During the first trimester, surgical abortions use gentle suction to remove a pregnancy from the uterus. Jennifer Gerson Uffalussy, Glamour, "How Much Does an Abortion Cost?," 26 Apr. 2019 Additionally, far more number of expecting mothers in Kerala enrol for early pregnancy care during their first trimester. Kuwar Singh, Quartz India, "What makes infant deaths five times as likely in Uttar Pradesh than in Kerala?," 26 June 2019 Medical terminations can occur in the early stages of the first trimester and can be accomplished by ingesting medicine. Christine Sexton,, "Broward doctor fined for giving woman surgical abortion rather than medication-induced procedure," 10 June 2019 But most of the cultures studied to date mimic the brain only in its first trimester of development. Quanta Magazine, "The Oldest Mini-Brains Have Lifelike Young Cells," 29 Aug. 2017 And sluggish was a considerable triumph, as the wrenching fatigue of my first trimester was slowly loosening its vise. Redbook, "The Shadow Side of Motherhood," 30 May 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'trimester.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of trimester

1821, in the meaning defined at sense 1

History and Etymology for trimester

French trimestre, from Latin trimestris of three months, from tri- + mensis month — more at moon

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Statistics for trimester

Last Updated

21 Jul 2019

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Time Traveler for trimester

The first known use of trimester was in 1821

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English Language Learners Definition of trimester

: a period of three months especially : one of three periods into which a woman's pregnancy is often divided
US : one of three periods into which an academic year is sometimes divided


tri·​mes·​ter | \ (ˈ)trī-ˈmes-tər How to pronounce trimester (audio) , ˈtrī-ˌ How to pronounce trimester (audio) \

Medical Definition of trimester

: a period of three or about three months especially : any of three periods of approximately three months each into which a human pregnancy is divided

More from Merriam-Webster on trimester

Rhyming Dictionary: Words that rhyme with trimester

Spanish Central: Translation of trimester

Comments on trimester

What made you want to look up trimester? Please tell us where you read or heard it (including the quote, if possible).


something desired as essential

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