course, coarse

Course or course means a path or way--
The obstacle course was a part of their military training.
The ship went off its course and they didn't know where they were.
They decided on a new course of action.
"The course of true love never did run smooth."
Course may mean the movement along a path or way, literally or figuratively--
The heart causes the blood to course through our veins.
The landslide forced the river to course through a narrow channel.

Course may mean a series or progression--
He is taking a course in physics.
The doctor prescribed a course of antibiotics.

Coarse or coarse ( rhymes with course ) means crude, rough,  or unrefined--
The cookbook says to use coarse meal to keep it from sticking.
This linen is of a very coarse weave.
His manners were coarse; he was not used to society.

Now that you know that, you can say--
"His father hoped that a course in public speaking would help to refine his coarse speech."

Note--"coarser" means more coarse--
This fabric is coarse, but the other is coarser.
"Courser" means a steed or mount--
"Away to the housetops his coursers they flew..."
Not to be confused with "corsair", a kind of ship--
She could see the sails of a corsair on the horizon.