Definition
A unit of speed equal to one nautical mile per hour. One knot is approximately 1.15 statute miles per hour or 1.852 kilometers per hour. Aircraft airspeed, groundspeed, and wind speed in aviation are almost always expressed in knots.
Plain English
A way of measuring how fast something is moving. One knot means traveling one nautical mile in one hour. It is the standard speed unit used in flying.
Context Anchor
Seen on airspeed indicators, takeoff and landing speeds, weather reports, and performance discussions such as liftoff speed in ground effect.
Derivation
The word comes from the old sailing practice of measuring a ship's speed by trailing a rope behind the vessel with knots tied at fixed intervals. Sailors counted how many knots passed through their hands in a set time, and that number became the ship's speed. Aviation inherited the unit from maritime navigation, since both use nautical miles tied to the size of the Earth.
Why Pilots Care
Knots keep speed references consistent with nautical-mile navigation and allow every pilot to read the same numbers on instruments and charts regardless of aircraft type.
Intuition Check
Do not read “knots” as rope knots here. In aviation, knots mean speed: nautical miles per hour.
Example Sentence 1
The reported wind at the airport was 15 knots from the west, so the pilot adjusted the takeoff plan accordingly.
Example Sentence 2
In cruise the airplane held a steady 110 knots groundspeed with a light tailwind.