The silent B: lamb, comb, thumb, debt, doubt
The silent B is the best place to see that not every silent letter is a lost sound. English has three kinds of silent B, and they have three different histories.
- A sound that was lost. Lamb, comb, climb and womb ended in a real "-mb" in Old English. Later Middle English reduced final -mb to -m, and the B fell silent.
- A letter added by analogy. Once "-mb said as -m" was a familiar pattern, writers began adding a B to words that had only ever had an M. Thumb (Old English þūma), crumb and limb got their B this way — it was never pronounced.
- A letter added by scholars. In the 1500s, writers who admired Latin put a B into debt and doubt to show their descent from Latin debitum and dubitare. English had borrowed these words from French as dette and doute, with no B — and no one ever said one.
lamb
In Old English, lamb was said with a final B. Later Middle English reduced -mb to -m, so lamb now rhymes with ham. Here is the story of the B.
- Then · Old English
- lamb
- Say it
- LAM
comb
Comb comes from Old English camb, an ancient word for "tooth", and its B was once pronounced. Here is how the B went silent and the vowel moved.
- Then · Old English
- camb
- Say it
- KOHM
thumb
Unlike lamb and comb, the B in thumb was never pronounced. Old English said þūma — the B was added in the late 1200s by analogy with other -mb words.
- Then · Old English
- þūma
- Say it
- THUM
debt
English borrowed debt from French as dette, with no B. Scholars added the B later to show off its Latin root, debitum. It was never pronounced.
- Then · Middle English
- dette
- Say it
- DET
doubt
Doubt was spelled doute in Middle English, with no B. Renaissance scholars added one to match Latin dubitare — but English never pronounced it.
- Then · Middle English
- doute
- Say it
- DOWT
One rule covers all of them
However the B got there, a B after M at the end of a word is silent in modern English, and so is the B before T in debt, doubt and subtle. When a suffix starts with a vowel the B usually stays silent too (climbing, bombing, plumber), but in a few Latin-based relatives it is pronounced: bomb is silent, bombard is not; crumb is silent, crumble is not.
Questions people ask
+Why is the B silent in lamb and comb?
Both once ended in a pronounced -mb. Later Middle English reduced final -mb to -m, and the spelling kept the B.
+Was the B in thumb ever pronounced?
No. Old English þūma had no B; it was added to the spelling in the late 1200s by analogy with words like lamb.
+Why is there a B in debt and doubt?
Scholars added it in the 1500s to show the Latin roots debitum and dubitare. The words came from French without a B, and it was never pronounced.
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