Why is there a silent b in debt?

The b in debt is silent because it was added to the spelling after the word had already entered English. It shows the word’s ancestry rather than its pronunciation.

The word arrived without a b sound

English borrowed the word through French, in a form resembling dette. During the Renaissance, scholars became increasingly interested in classical Latin. They inserted a b to display the connection with Latin debitum.

The spelling changed, not the speech

By then, speakers had long pronounced the word without /b/, and the added letter did not alter that habit. The related word debit does pronounce its b, which makes the family resemblance visible but does little to help learners spell debt.

Nederlandse uitleg

In het Nederlands: de b werd later toegevoegd om de link met het Latijnse debitum te laten zien. De uitspraak veranderde niet, dus de b bleef stil.

Try it yourself

Say these aloud: debt, doubt and subtle. Each contains a silent b, although the details of their histories differ.

Source: Merriam-Webster. Featured photograph by Brett Jordan on Unsplash.