Trimester

Trimester or Trimestre may refer to:
 * Academic term, a trimester system divides the academic year into three terms
 * Trimester (pregnancy) in humans, where the time of pregnancy is divided into three terms of 13 weeks to refer to the fetus's development
 * The trimester framework in Roe v. Wade, which organized constitutional issues in abortion law according to trimesters
 * A period of three months (Latin tri +mensis=month or moon) In Europe, where financial years start on 1 January each year, often Jan+Feb+Mar etc.