Élisions des Déterminants devant Voyelle

French phonology refuses to put a determiner-final vowel next to a noun-initial vowel. To enforce this, the language deploys three different repair strategies — apostrophe-elision, full form-swap, and outright blocking when the h is aspirated — and each determiner uses a slightly different one. This page collects every determiner that changes shape before a vowel, explains why each one changes the way it does, and gives you the closed list of h aspiré words that defeat the rule. Once you internalise this, the otherwise mysterious leap from le ami to l'ami and from ce ami to cet ami becomes a single, predictable phonological reflex.

The general principle

French speech operates by a near-absolute preference: every syllable should begin with a consonant. When two short grammatical words abut and the boundary would create a vowel-vowel hiatus, French repairs the boundary. With determiners the repair takes three forms.

• Elision — the determiner's final vowel is dropped and replaced with an apostrophe. Le → l', la → l', de → d'. The apostrophe is written; the vowel is gone in speech as well.
• Form-swap — the determiner is replaced by a different form ending in a consonant. Ce → cet, ma → mon, ta → ton, sa → son.
• No change needed — the determiner already ends in a consonant or in s that liaises into the next vowel. Les amis /le‿zami/, un ami /œ̃‿nami/, des amies, mes amies, nos amis.

What never happens is hiatus. You will never hear a careful speaker say le ami or ma école; the sound sequence is simply ungrammatical in the spoken language.

Le and la elide to l'

The definite article is the most familiar case. Both le (m. sg.) and la (f. sg.) drop their vowel before any word starting with a vowel sound or h muet. The result is written l' and pronounced as a single syllable with the following noun.

The article still encodes the gender — it is just no longer visible on the determiner itself. L'eau is feminine, l'arbre is masculine, and you have to know which from context, agreement, or memorisation. There is no spelling difference between elided masculine l' and elided feminine l'.

The plural les is unaffected by elision: it ends in s, and that s simply liaises into the following vowel. Les amis is pronounced /le‿zami/; les hommes is /le‿zɔm/. No apostrophe ever appears with les.

The partitive de l' and de la

The partitive article, used for indefinite quantities of mass nouns, behaves the same way. Before a vowel or h muet, the masculine du and feminine de la are both replaced by de l'.

The masculine partitive du is itself a contraction of de + le, and the feminine partitive is the unreduced de la. Before a vowel, both surface as de l' — the l' preserving the merged contraction-and-elision in a single form. The plural partitive des is not affected: des amis, des œufs, with simple liaison.

Ce becomes cet — a form-swap, not an elision

The masculine singular demonstrative ce does not elide. Instead, French swaps it for the longer form cet before a vowel or h muet. There is no apostrophe; cet is a full word with a pronounced final /t/ that liaises into the following noun.

The reason for the swap rather than elision is historical. Old French had cest (masculine) and ceste (feminine), both ending in a consonant cluster. Modern French shortened the masculine to ce before consonants but kept the older form cet before vowels — exactly the form that delivers the consonant onset the next word needs. So cet is not a contraction of ce + something; it is the survival of the older, fuller form, conserved precisely because French needs a consonant-final variant.

The feminine cette is invariable: it always ends in a pronounced /t/, so no swap is necessary. Cette amie, cette histoire, cette école — all simply cette. The plural ces takes liaison: ces amis /se‿zami/.

Mon, ton, son before feminine vowels

The feminine singular possessives ma, ta, sa all end in /a/. Before a vowel or h muet, French swaps them for the masculine forms mon, ton, son. The noun stays feminine; only the determiner changes shape.

The plural possessives mes, tes, ses, nos, vos, leurs are unaffected — they all end in s and liaise. The first- and second-person plural-possessor forms notre, votre, leur (which mark a singular noun belonging to a plural possessor) end in a consonant and never need to change either. So the entire scope of the swap reduces to the three feminine singulars ma → mon, ta → ton, sa → son, before vowel-initial words. For a deeper treatment of this specific rule, see mon-vs-ma-with-vowels.

Du, de la, des: how the partitive system handles vowels

The partitive forms — du (masc. sg.), de la (fem. sg.), des (plural) — distribute according to the same vowel-avoidance principle as the definite article. Before a vowel or h muet, both du and de la collapse to de l'; only des keeps its shape, because the final s simply liaises into the next vowel.

The pattern is symmetrical with what le, la, l' do for the definite article: a single l' form covers both genders before vowels, and the gender becomes invisible on the surface determiner.

Before h aspiré, the partitive keeps its consonant-onset behaviour and uses du or de la with no elision:

What counts as a vowel: h muet vs h aspiré

Both kinds of h are silent in modern French — neither is pronounced as a sound. But for the purposes of elision, liaison, and the form-swap rules above, they behave very differently.

• H muet (mute h) is treated as if it were not there. The word behaves like a vowel-initial word: l'homme, l'hôtel, mon habitude, cet hiver, de l'huile, les hôpitaux with liaison.
• H aspiré (aspirated h) is treated as if a real consonant were present. It blocks elision, blocks liaison, and blocks every form-swap discussed on this page.

The two kinds of h are not predictable from spelling, and you have to learn them by exposure and reference. Most h words in French are h muet; the h aspiré set is a finite list of mostly Germanic, Frankish, and English borrowings. The most common h aspiré words are:

Before any of these, every rule on this page is suspended. Le héros (not l'héros), la haine (not l'haine), ce héros (not cet héros), ma haine (not mon haine), de la haine (not de l'haine).

Compare side by side what the h muet counterparts look like:

Dictionaries mark h aspiré with a special sign — usually an asterisk, dagger, or apostrophe before the headword. The Petit Robert, for instance, prints 'haine with a leading apostrophe. When in doubt, look it up; the list is bounded and worth memorising for the most frequent fifteen or twenty entries.

Comparison with English

English has nothing structurally comparable. The closest analogue is the indefinite article a → an before vowels, but English does this only with that one determiner and only by adding a single consonant. No English determiner swaps to a different form; no English determiner elides its vowel and writes an apostrophe. Definite the is invariant in spelling — the apple — though pronunciation does change from /ðə/ to /ði/ before a vowel, a quiet phonological echo of the same hiatus-avoiding instinct.

The deeper insight for English speakers is that French treats determiners as words that must "fit" the next word phonologically. English treats them as fixed lexical items. Once you stop expecting le, la, ce, ma to remain rigid, the swaps and elisions become simple consequences of a constant rule: never let a vowel sit next to a vowel across a determiner-noun boundary.

Common Mistakes

The fifth and sixth mistakes are the most common at A2 level. Once a learner has internalised the elision rule for l' and the swap for cet/mon, the temptation is to apply it everywhere a written h appears. The h aspiré list defeats this generalisation, and there is no way around learning the list. The good news is that the most frequent h aspiré words come up in everyday vocabulary — héros, haine, honte, haut, haine, hibou, hasard — so a few weeks of careful reading will give you the most useful entries by heart.

Key takeaways

The umbrella rule is simple: French does not allow a determiner-final vowel before a noun-initial vowel. The repair strategies divide cleanly by determiner. Definite articles le, la elide to l', and the partitive du, de la both collapse to de l', before vowels and h muet. The masculine demonstrative ce form-swaps to cet. The feminine singular possessives ma, ta, sa form-swap to mon, ton, son. The plurals les, des, mes, tes, ses, nos, vos, leurs and the singular notre, votre, leur, cette, un, une simply liaise into the next vowel. H muet triggers all of these; h aspiré blocks all of them and is restricted to a closed list of borrowings. Master the eight or ten most frequent h aspiré words, and the rest of the system reduces to a single phonological reflex you will eventually apply without thinking.