These words sometimes sound the same but have different meanings.

canvas is used for tarps
canvass is to solicit voters

capital is a city designated as a legislative seat
capitol is the building located in the capital city

cite is to list a source in a book
site is a location
sight is the ability to see

clothes are what we wear
close is what you do to a door after exiting

course is the route taken by cross-country runners
coarse is sandpaper with large particles

cursor is a moving icon driven by a pointing device
curser is one who curses