Liaison
Summary
Liaison pronounces a normally silent final consonant and links it to a following word that begins with a vowel sound.
Explanation
Many French words end in a consonant that is silent in isolation, but when the next word starts with a vowel sound (or a mute h), that consonant is pronounced and attached to the following syllable. les amis sounds like /lez‿ami/ ("lay-za-mee"), as if the s belonged to amis. This linking is called liaison, and it is one of the main reasons spoken French sounds so smooth and connected.
The liaison consonant is not always read with its usual value. The letters s and x surface as /z/ (les‿amis, deux‿heures /døz‿œʁ/), d surfaces as /t/ (un grand‿homme /ɡʁɑ̃t‿ɔm/), and f surfaces as /v/ in a few set phrases (neuf‿heures /nœv‿œʁ/, neuf‿ans). The letters n, r, t, p keep their own sound (un‿ami /œ̃n‿ami/, premier‿étage, petit‿enfant). A nasal vowel often partly denasalises and the /n/ is added: bon‿ami is /bɔn‿ami/.
Liaisons fall into three classes. Obligatory liaisons must be made: after determiners (les, des, un, ces, mon, deux), between a subject or object pronoun and its verb (nous‿avons, ils‿ont, on‿a, vous‿en avez), after short prepositions and adverbs (en, dans, sans, très, bien, plus), and in many fixed phrases (de temps‿en temps, les États‑Unis). Optional liaisons (after a plural noun before an adjective, after être) are made in careful or formal speech and dropped in casual speech. Forbidden liaisons must never be made.
The forbidden cases matter as much as the obligatory ones. Never link after the conjunction et ("and"): un homme et‿une femme is wrong; say et une /e yn/ with a clean break. Never link before an aspirate h (les héros /le eʁo/, en haut /ɑ̃ o/). Never link after a singular noun before its verb or adjective (un étudiant‿intelligent is wrong), and avoid liaison after the interrogative inversion -t in writing-style speech in some set cases. As a learner, the safe strategy is to drill the obligatory liaisons first, observe the forbidden ones, and treat optional ones as a register choice.
A related but distinct phenomenon is enchaînement, where a consonant that is already pronounced in isolation simply re-syllabifies onto the next vowel (elle aime → /ɛ‿lɛm/). Liaison differs because it resurrects a consonant that would otherwise be silent. Both contribute to the seamless flow of French, but only liaison is governed by the obligatory/optional/forbidden system above, so it is the one worth studying explicitly.
Examples
les amis — the friends (Obligatory liaison after the article; final s of les → /z/: /lez‿ami/.)
un grand homme — a great man (Silent d of grand surfaces as /t/ in liaison: /ɡʁɑ̃t‿ɔm/.)
Ils ont deux enfants. — They have two children. (Pronoun+verb and number liaisons: ils‿ont /ilz‿ɔ̃/, deux‿enfants /døz‿ɑ̃fɑ̃/.)
Il est neuf heures. — It is nine o'clock. (f of neuf becomes /v/ before heures: /nœv‿œʁ/ (also neuf‿ans).)
un homme et une femme — a man and a woman (Forbidden liaison after et: say /e yn/, never /e‿tyn/; but un‿homme links: /œ̃n‿ɔm/.)
Common mistakes
un homme et‿une femme /ɛ̃nɔm e‿tyn fam/
un homme et une femme /ɛ̃nɔm e yn fam/
Liaison is forbidden after the conjunction et ("and"). Although et ends in a normally silent -t, that -t is never linked to a following vowel: et une is /e yn/ with a clean break, never /e‿tyn/. Learners who over-apply liaison often add a wrong /t/ here. Note the contrast with the obligatory liaisons around it: un homme is /ɛ̃nɔm/ (n linked), but et une stays unlinked.
Prerequisites
Related rules
liaisonconnected-speechconsonantssilent-letters