Is the word sand a homograph?

Homographs are words that are spelled the same but are pronounced differently and have different meanings. Sand can mean a grainy substance or to smooth something.

Yes, the word "sand" is indeed a homograph. Homographs are defined as words (usually pairs) having the same spelling. They aren’t necessarily pronounced the same. In fact some words completely change their meaning when there is a shift in the pronunciation. But they should always be used in the proper context, since they will have different meanings. In this case, "sand" is a homograph since it can be used either "put or sprinkle sand", "polish using a sandpaper", or "a granular substance formed from soil erosion".