Quick answer
Coarse means rough in texture or crude in manner — coarse sand, coarse language. Course covers a route, a series of lessons, part of a meal, and the phrase "of course". Only one of them describes texture, and it is the one with the A.
The core difference
Homophones with one narrow meaning and one very broad one.
- coarse — rough, crude: coarse grain, coarse humour.
- course — a route, a programme of study, a meal part, a golf course, "of course".
The reliable check
Coarse has an A, and so does rough… which does not help. Better: coarse is almost always an adjective describing texture or manner. If the word is a noun, it is nearly always course.
Where the error shows
Frequently asked questions
Which spelling means rough?
Coarse, with the A.
Is it coarse or course grind?
Coarse grind. Course would mean a route or a programme of study.
What is the quickest test?
If it is describing texture or manner, use coarse. If it is a noun, it is almost always course.