Originally Posted by
FBinNY
Not quite. knots are nautical miles per hour. A nautical mile is 1.15 (land) miles, so a knot = 1.15mph. The issue isn't the power source (sail, wind) but whether you're in a boat at sea.
And yet airplanes also use the term "knot" when referring to wind speed and air speed... so indeed the term is NOT limited to water based craft. The nautical mile is the key here... and the key is that a "nautical mile" is roughly equivalent to one minute of arc of latitude.
The nautical mile remains in use by sea and air navigators worldwide because of its convenience when working with charts.
http://en.wikipedia.org/wiki/Nautical_mile