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

Early vaccinations can be given in July and August for children who only need one dose and for people who are in their third trimester of pregnancy at that time, according to the agency. —Angelica Stabile, Fox News, 18 Sep. 2024

However, abortions in those cases must be completed in the first trimester and the pregnant person must report the incident to law enforcement. —Aria Bendix, NBC News, 12 Nov. 2024

The very small number that take place in the third trimester are usually done because of dangerous medical conditions. —Emma Specter, Vogue, 11 Sep. 2024

During the first trimester, the current leave period for either category will be doubled from five to 10 days. —Gordon G. Chang, Newsweek, 31 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