trimester

noun

tri·​mes·​ter (ˌ)trī-ˈme-stər  ˈtrī-ˌme- 

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

Every trimester of pregnancy is different, and so are the potential risks of having the flu. —Laura Dorwart, Verywell Health, 24 Oct. 2024

To best protect newborns against whooping cough, the CDC urges pregnant people to get the Tdap vaccination during their third trimester. —Don Rauf, EverydayHealth.com, 16 Oct. 2024

More than 80% of abortions occur in the first nine weeks of pregnancy, and 6% occur during the second trimester. —Tribune News Service, The Mercury News, 14 Oct. 2024

In the first trimester, hCG helps the body create necessary reproductive hormones, like progesterone. —Sarah Bradley, Health, 9 Oct. 2024

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

Phrases Containing trimester

• fourth trimester

Medical Definition

trimester

noun

tri·​mes·​ter (ˈ)trī-ˈmes-tər  ˈtrī-ˌ 

: 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