au · aux · du · des

In one line

When à or de meets le or les, they fuse into one word. With la and l', never.

The table

Only the first and last columns fuse.

And the four you must treat as forbidden

Masculine and plural fuse. Feminine does not.

au is not one word — it is two separate decisions stuck together

This is the most important sentence on the page. When you write Je vais au parc, you have really made three separate decisions:

Only step 3 is the rule on this page — and it is the one step that needs no thought. The real difficulty is in steps 1 and 2.

If you got it wrong somewhere, it was almost always step 1 or step 2, not the contraction.

Step 1 — where that à came from

It has two sources, and you need to know which one you are dealing with.

But first: make sure you can even see that there is a slot

The worst mistake is not choosing the wrong preposition — it is writing none at all.

Verbs of movement and location in French never take a bare place noun. There is always a preposition in between.

aller is intransitive; it has no direct-object slot. The place is not "the thing you go", it is "where you go", and French always marks that:

Why that empty slot is invisible to you

Two reasons, and neither is carelessness.

Reason one — your first language drops it. English does this too, more often than you notice:

And languages that drop it everywhere — Persian, Turkish, Hindi, Chinese — hit this on every sentence, not just a few idioms.

Reason two — au hides that à. The correct answer is au festival, and you can see neither à nor le inside it. So even staring at the right form, the preposition you omitted is not visible in it.

Safety rule: until you have written a preposition after aller · venir · arriver · partir · sortir · rentrer, the sentence is not finished.

And watch for the two-layer error

je veux aller la festival contains two mistakes, not one — and because they sit on top of each other they are hard to spot:

Then step 3 melts the two together: à + le ← au festival.

A gender tip that settles this one: nouns ending in -al are almost always masculine — le festival · le journal · le cheval · le total · l'hôpital. (The plural of festival is the exception: les festivals, not festivaux.)

a) The verb demands it

In French the preposition is part of the verb itself — exactly like English phrasal verbs. No English speaker works out from first principles why you look after a child but look for a key; you learn the pair as a unit. French à and de are the same thing. Memorise them with the verb, not with the meaning:

The trap for an English speaker. English adds a preposition to several verbs where French adds nothing: you look at a film, wait for the bus, listen to music, pay for a ticket, ask for the bill. In French all five are bare — regarder le film, attendre le bus, écouter la musique, payer le billet, demander l'addition — and so there is nothing to contract. Do not translate the English preposition. The full list of verbs is in verbe-prepositions.

b) The meaning demands it

When no verb is involved, the meaning itself picks the preposition:

The short version: à means "to / at", de means "from / of". The detail is in a-ou-de.

Step 2 — and where that le came from

From the gender of the noun, and it has nothing to do with the verb:

Look closely at hôtel: it is masculine, but because it begins with a vowel it takes l', and l' never fuses. So being masculine is not enough — it has to be a full le.

And this is why au hides the gender

In au parc the le is invisible, but it is in there. That is useful when reading — you can run the rule backwards:

So au is telling you the noun is masculine. If you see au somewhere and thought the noun was feminine, one of the two is wrong.

The hidden source of du — compound prepositions

Any preposition ending in de takes the same contraction. Nobody teaches you these, and they are where most of the mistakes come from:

And one with à: jusqu'à (as far as) → jusqu'à + le bout → jusqu'au bout.

Exceptions

There are none. This is one of the very few French rules that works one hundred per cent of the time.

Only one thing looks like an exception and is not: when there is no article after de at all, there is nothing to contract, and de merely elides before a vowel:

Examples

Common mistakes

And why they fused at all

In one sentence: à le was pronounced al a thousand years ago, and in Old French any l that fell in front of a consonant melted into a u sound. So al became au.

The same event that turned cheval into chevaux and bel into beau. Which means au is not a grammatical rule — it is a worn-down word whose spelling froze.

And why did la survive? Because the e of le was weak and dropped, leaving that l alone in front of a consonant, where it melted. The a of la was strong and did not drop, so its l was never in that position.

The three-second checklist

0. Is a preposition needed at all? ← after a verb of movement or location (aller · venir · partir · sortir · rentrer) always yes. This is the step learners skip. 1. Which preposition? ← the verb decides (aller à · parler de · regarder nothing), or the meaning does (à = to, de = from). And remember compound prepositions end in de too. 2. Which article? ← from the gender of the noun: le · la · l' · les 3. Now contract ← if it came out le or les, fuse them; if la or l', leave them alone

And do not forget: this contraction is not optional. In English you can choose not to shorten do not to don't, but here à le is not a possible form at all — not in formal writing, not in speech, not in poetry.