Accord avec combien de COD

In a standard sentence like J'ai mangé des pommes, the apples come *after* the verb. The verb mangé stays the same. But when you use combien de, the apples move to the front of the sentence. Because the object (the apples) now appears *before* the verb, the verb has to agree with it. It’s a bit like a mirror. If the noun in front of the verb is feminine, you add an e. If it’s plural, you add an s. If it’s both, you add es. You are basically giving the verb a heads-up about what it's talking about before it even gets to the action. It’s a polite way to keep your sentences organized and stylish.

1. 1To master this, just follow these simple steps:
2. 2Start your sentence with Combien de (or Combien d' if the next word starts with a vowel).
3. 3Place the noun you are counting right after it.
4. 4Add your helper verb avoir (conjugated to match the subject).
5. 5Add the subject (the person doing the action).
6. 6Write the past participle.
7. 7Add the agreement to the end of that participle based on the noun from Step 2.
8. 8Masculine Singular: No change (e.g., mangé)
9. 9Feminine Singular: Add e (e.g., mangée)
10. 10Masculine Plural: Add s (e.g., mangés)
11. 11Feminine Plural: Add es (e.g., mangées)

You use this rule every time you ask a question about quantity in the past. Imagine you are at a job interview and they ask, "How many projects have you finished?" Since projets is masculine plural, the verb fini becomes finis. Or maybe you are at a café and your friend asks, "How many coffees did you drink?" Since cafés is masculine plural, bu becomes bus. It applies to any scenario where you are counting things that have already happened. It’s very common in travel situations, like asking how many photos someone took or how many cities they visited. It’s the grammar equivalent of checking your receipts after a big shopping trip.

Don't get overexcited and start adding e and s everywhere! This rule only applies if the noun comes *before* the verb. If you are just making a normal statement like J'ai acheté trois voitures, no agreement is needed. Also, if you use the pronoun en to replace the noun (e.g., Combien en as-tu acheté ?), the agreement usually disappears. Think of en as a grammar invisibility cloak that hides the gender and number from the verb. Finally, this rule is specifically for the helper verb avoir. If you are using être, you are following a different set of rules entirely. Keep it simple: no noun in front, no extra letters on the back.

The most common slip-up is simply forgetting the agreement because we don't do this in English. You might say Combien de lettres as-tu écrit ? but in French, lettres is feminine plural, so it must be écrites. Another mistake is trying to agree with the subject (the person) instead of the object (the things). If a girl asks, "How many books did I buy?", the verb agrees with the *books*, not the girl. It’s a common trap! Also, watch out for words that sound the same but are spelled differently. Mangé, mangée, and mangées all sound identical, but the spelling matters for your written French. It's like wearing mismatched socks; people might not hear it, but they'll definitely see it.

Compare this to the standard passé composé. In Tu as vu les filles, the verb vu is neutral. But in Combien de filles as-tu vues ?, the es is mandatory. It’s also different from agreement with être. With être, the verb always agrees with the subject (the person doing the action). With combien de and avoir, we only care about the object being counted. Think of avoir as a bit more selfish; it only agrees if the object gets in its way at the start of the sentence. If the object stays in the back, avoir ignores it completely. It’s a small distinction that makes a huge difference in how "native" you sound.