Just to ad my 2cents worth, I thought these were the definitions. Homophone A word which sounds the same as another, but is written differently. So, Sew
Homograph A word written the same as another, but pronounced differently. wind (air movement) and wind (to tension a spring).
My understanding is that homonym includes both of these categories.
Of course, I could be wrong. I thought I was once, but i was mistaken. :o) Eddie