The B in Thumb Was Never Pronounced
The thumb is the short thick digit of the hand. Its silent B was added by scribes centuries after the word existed.
The thumb is the short thick digit set apart from the fingers. Old English *thuma* had no B at all; scribes added it in the 1500s by analogy with *dumb* and *limb*, and it has never been pronounced. The same fashion produced the B in *crumb*. Anatomically the thumb is what makes human hands distinctive: it is *opposable*, able to touch each fingertip, which allows a precision grip that most primates cannot match.
- The hand's short digit. *A sore thumb.*
- Opposable — able to touch the fingers. *Opposable thumb.*
- To thumb through. *Thumb the pages.*
- Rule of thumb — a rough method. *A rule of thumb.*
- Old English — *thuma*. *The source.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | thumb | A thumb. |
| Plural | thumbs | Thumbs. |
| Verb | thumb | Thumb a lift. |
| Compound | thumbnail | A thumbnail. |
| Old English | thuma | Thumb. |
- He hit his thumb with the hammer.Anatomy.
- She thumbed through the magazine.Verb.
- As a rule of thumb, allow an hour.Idiom.
Thumb phrases
- Rule of thumb — a rough practical method
- Stick out like a sore thumb — be conspicuously out of place
- Under someone's thumb — completely controlled
- Green thumb — American for green fingers
- Thumbnail sketch — a very brief description
Old English *thuma*, of Germanic origin, from a root meaning swollen or thick. The B was added by scribes in the 1500s.
Why does thumb have a silent B?
Scribes added it in the 1500s by analogy with words like dumb and limb. It was never pronounced.
What makes a thumb opposable?
A saddle joint at its base lets it rotate to touch each fingertip, giving humans a precision grip.