I pretty much agree with Jamie, but if I had to give my own numbers:

Light: 0 to 8mph

Medium: 8 to 18mph

Heavy: 18mph and above

When I'm by myself I don't like wind over 22mph. But if you have a experienced crew, then "terror" sailing can be quite entertaining. In the "old days" my sailing partner and I would pray for the local weatherman to say "inland lake wind warnings". But he got married, and his wife frowns on men behaving badly.

One thing I really hate is a "punchy" wind. This is where sudden gusts exceed the base wind by a lot.-It is as if the jolly green giant put his fist in your sail from out of nowhere. Once, I and my sailing partner were moving along in a moderate breeze and a gust instantly knocked the boat over, -and we were sitting in the middle of the main above the numbers wondering HOW we got there.