trimestre

Trimestre is a term used to denote a period of three months, i.e., one third of a calendar year. The word derives from Latin tri- meaning three and mensis meaning month, and it appears in several Romance languages with the same core meaning. In modern usage, the term is applied in contexts where the annual cycle is divided into three segments.

In obstetrics, pregnancy is commonly divided into three trimesters, each representing roughly three months of gestation. The first trimester typically covers the early weeks up to about week 12, the second from week 13 to 26, and the third from week 27 until birth; exact cutoffs can vary by country and medical guideline.

In education, some school systems use a trimester calendar, dividing the academic year into three terms of about 12 to 14 weeks each. This contrasts with semester systems, which divide the year into two terms. The use and length of trimesters vary by country and institution.

Outside medicine and education, the term trimester or trimestre may be used in budgeting, business reporting, or calendar planning to denote any three-month period within a year. The English term trimester is cognate with the French trimestre and the Spanish trimestre, and similar forms appear in other Romance languages. The word is distinct from quarter, though usage can overlap depending on the organizational system.