Trimester and semester are easily confused words.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It’s suggesting what word you may want to save time, but quite often, its suggestions are pretty off base. They don’t help you out, but they do make you laugh.
Trimester is a noun. It means a 3-month period.
Human pregnancy lasts nine months, which are divided into three trimesters. Each trimester involves developmental milestones. Click here to read more.
[The prefix “tri-” typically means “three” in many English words: A trident is a tool with three tines. A triangle is a shape with three sides. A tri-county area involves three US counties where the population density is high; people move within those three counties to live, work, and play. Tri-county areas can cross state lines.]
Semester is a noun. It means a 15 to 18 week period of time making up half a school year in US public schools. Private schools and foreign schools have different practices for school terms.
The following story uses both words correctly:
Thijs had just finished his final semester at college when he learned that his fiancé was expecting. She was three weeks into her first trimester. It was proving difficult to find a residency in dentistry in a slow economy. So he took a position in his family’s flower and landscaping business. He would remain there for 10 years.