A Knot Is a Unit of Speed Named After a Rope
A knot is a fastening in rope, and also one nautical mile per hour. The unit is named after a measuring method.
A knot is a fastening made by looping and tightening rope, and a unit of speed of one nautical mile per hour. The unit is named after the method: sailors threw a weighted log overboard attached to a line knotted at regular intervals, and counted how many knots ran out in a fixed time measured by sandglass. The count gave the speed directly, and the log book took its name from the same device. Saying *knots per hour* is therefore wrong, since the hour is already included.
- A rope fastening. *Tie a knot.*
- A unit of speed. *Twelve knots.*
- A wood flaw. *A knot in the plank.*
- Log — the device behind it. *A ship's log.*
- Old English — *cnotta*. *The source.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | knot | A knot. |
| Plural | knots | Knots. |
| Verb | knot | Knotting. |
| Adjective | knotty | Knotty. |
| Old English | cnotta | A knot. |
- Tie a proper knot.Rope.
- Making fifteen knots.Speed.
- Knots per hour is wrong.Usage.
How the chip log worked
- A weighted wooden chip was thrown astern
- It stayed roughly still in the water as the ship moved away
- The attached line was knotted at regular spacing
- A sandglass timed a fixed interval
- Counting knots run out gave the speed directly
Old English *cnotta*, of Germanic origin, related to Dutch *knot*.
Why is speed at sea measured in knots?
From a line knotted at intervals, thrown overboard with a weighted log. Counting the knots that ran out in a timed interval gave the speed.
Is knots per hour correct?
No. A knot already means one nautical mile per hour, so the phrase repeats the time unit.