A Fathom Is the Span of Outstretched Arms
A fathom is six feet of water depth. The unit was originally the distance between a person's fingertips, arms outstretched.
A fathom is a nautical measure of six feet, used for water depth. The unit is a body measurement: Old English *fæthm* meant the outstretched arms, and a fathom was the span from fingertip to fingertip. Sailors measured depth by hauling in a marked line hand over hand, and each arm-span was one fathom.
- Six feet of depth. *Twenty fathoms.*
- To understand. *I cannot fathom it.*
- To measure depth. *Fathom the channel.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | fathom | Ten fathoms deep. |
| Plural | fathoms | Six fathoms. |
| Verb | fathom | Fathom his reasons. |
| Adjective | unfathomable | An unfathomable choice. |
| Related | sounding | Take a sounding. |
How it is used in a sentence
- Full fathom five thy father lies.Shakespeare, The Tempest.
- I cannot fathom why.Understand.
- A fathom is six feet.About 1.83 metres.
Measures from the body
- Fathom — the span of outstretched arms
- Foot — the length of a foot
- Cubit — elbow to fingertip
- Hand — four inches, still used for horses
- Span — thumb tip to little finger tip, about nine inches
From Old English *fæthm*, the outstretched arms or an embrace. The sense of understanding comes from sounding the depth of something.
Why does fathom mean to understand?
From measuring depth by sounding. To fathom something is to get to the bottom of it.
Is the fathom still used?
Yes, on nautical charts in some countries, though metres are now standard on most modern charts.