Unfaithful

How to spell unfaithful

10 letters · 3 syllables

How to pronounce unfaithful

Say the part in capitals loudest.

What does unfaithful mean?

1. adjectiveNot loyal, especially having a romantic or sexual relationship outside a committed partnership.
2. adjectiveFailing to represent something accurately or to keep to an original.

Unfaithful in a sentence

• She filed for divorce after discovering her unfaithful husband.

• The translation was unfaithful to the author's original meaning.

• A single unfaithful partner can shatter years of trust.

• Critics called the film an unfaithful adaptation of the beloved book.

Where does unfaithful come from?

Language of origin: French

This word is built from three layers of English word-making. At its heart sits 'faith', which English took from Old French 'feid' or 'fei' in the 1200s, itself descended from the Latin 'fides', meaning 'trust' or 'belief'. To that root English added the native suffix '-ful', meaning 'full of', producing 'faithful' (full of loyalty) by the late Middle Ages. The negating prefix 'un-', one of the oldest and most productive prefixes in English from its Germanic roots, was then attached to flip the sense to 'not loyal'. The same Latin 'fides' survives in relatives such as 'fidelity', 'confide', and 'bona fide', so the idea of trust runs quietly through all of them. The spelling trap is the silent stretch in the middle: 'fai' keeping its old French vowel cluster, and the single 'l' at the end, since '-ful' as a suffix never doubles.

How the word is built

• un- (not)
• faith (loyalty, trust)
• -ful (full of)