trimester

noun

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

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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Pettersen, a Democrat serving Colorado’s third Congressional District, has been unable to cast her vote since January 13, the last day she was cleared by her doctor to fly in her final trimester of pregnancy. Glamour, 23 Jan. 2025 The woman is in her third trimester and is concerned her child would be denied citizenship. Kristen Waggoner, Newsweek, 21 Jan. 2025 The mom-to-be is in her third trimester, the lawsuit says. Russell Contreras, Axios, 21 Jan. 2025 On Wednesday, the zoo announced the upcoming addition to its seven dolphins as 37-year-old Allie enters her second trimester of pregnancy. Adriana Pérez, Chicago Tribune, 15 Jan. 2025 See all Example Sentences for trimester 

Word History

Etymology

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

First Known Use

1821, in the meaning defined at sense 1

Time Traveler
The first known use of trimester was in 1821

Dictionary Entries Near trimester

Cite this Entry

“Trimester.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/trimester. Accessed 10 Feb. 2025.

Medical Definition

trimester

noun
tri·​mes·​ter (ˈ)trī-ˈmes-tər How to pronounce trimester (audio) ˈtrī-ˌ How to pronounce trimester (audio)
: 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
Last Updated: - Updated example sentences
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