Learn Hardcore French: Paul mange une tranche de pain avec du fromage.

After words that express a quantity or portion (like une tranche, un morceau, un verre, un kilo, etc.), French normally uses de + noun without an article for a general meaning:

une tranche de pain – a slice of bread
un morceau de fromage – a piece of cheese
un verre de lait – a glass of milk

Une tranche du pain is grammatically possible but would mean a slice of the bread (referring to some specific bread already identified in context). In most neutral sentences, you just want a slice of bread, so you use une tranche de pain.

Why do we have de before pain but du before fromage?

They come from two different structures:

une tranche de pain
- de is used because tranche is a measure / portion word.
- Pattern: [quantity word] + de + [noun] → tranche de pain.
avec du fromage
- Here there is no quantity word; du is the partitive article (or de + le).
- It expresses “some cheese” in a general, non-countable way.

So:

de pain: because of the quantity expression (une tranche de …)
du fromage: because of the partitive article (“some” cheese)

What exactly does du mean in du fromage? Is it the same as de le?

Yes, du is the contraction of de + le:

de + le fromage → du fromage

In this sentence, du is functioning as a partitive article, which usually translates as “some” in English:

du fromage – some cheese
de la salade – some salad
de l’eau – some water
des pommes – some apples

So avec du fromage means “with some cheese” (not necessarily a whole cheese, just an unspecified amount).

Why is it du fromage and not le fromage or un fromage?

It depends on what you want to say:

du fromage – some cheese (an unspecified amount, what you normally eat)
le fromage – the cheese (specific: the one we know about or already mentioned)
un fromage – a cheese (a whole cheese as an item, e.g. a whole Camembert)

In Paul mange une tranche de pain avec du fromage, we are talking about some cheese in general, so du fromage is the natural choice.

How do we know that pain and fromage are masculine?

French gender is mostly lexical (you have to learn it with each noun).

For these words:

le pain – the bread (masculine) → du pain, un pain
le fromage – the cheese (masculine) → du fromage, un fromage

Clues in this sentence:

You see du fromage: du = de + le, so fromage is masculine.
If you wrote le pain, you’d also see it is masculine: le pain, not la pain.

Unfortunately there is no reliable rule that “-age” or “-in” always means masculine, but many nouns with these endings are masculine, so that can help a little. Ultimately, you need to memorize le pain and le fromage as masculine.

Why is tranche singular and not plural (tranches)?

Because we are talking about one slice:

une tranche de pain – one slice of bread
des tranches de pain – (some) slices of bread

The article une is singular, so tranche must also be singular.
If Paul were eating several slices, you would say:

Paul mange des tranches de pain avec du fromage.

Could we also say Paul mange du pain avec du fromage? What is the difference in meaning?

Yes, that is correct French, but the nuance changes:

Paul mange une tranche de pain avec du fromage.
→ Focuses on one slice of bread.
Paul mange du pain avec du fromage.
→ He is eating some bread with cheese, without specifying the form (slice, piece, etc.).

Both are grammatical; une tranche is just more precise about the shape/portion.

Why do we use avec and not et between pain and fromage?

Both are possible, but they don’t say exactly the same thing:

avec = with → suggests bread accompanied by cheese, often together (bread + cheese as a combination).
- une tranche de pain avec du fromage = a slice of bread with cheese (on it or eaten together).
et = and → simply lists two things, not necessarily combined.
- Paul mange du pain et du fromage. = Paul is eating bread and cheese (they could be separate).

In your sentence, avec emphasizes the idea of bread served with cheese.

Could we say Paul prend une tranche de pain avec du fromage instead of mange?

Yes, that is possible and common in some contexts.

manger = to eat (focus on the action of eating)
prendre = literally “to take”, but often used like “to have” (for food and drink), especially when ordering or talking about meals:
- Je prends un café. – I’ll have a coffee.
- Elle prend une soupe. – She’s having a soup.

Paul prend une tranche de pain avec du fromage would sound like:

Paul is having a slice of bread with cheese (e.g. as part of a meal, or ordering it).

How would the sentence change if we were talking about several people (they) instead of Paul?

You would change the subject and the verb, but the rest stays the same:

Paul mange une tranche de pain avec du fromage.
Ils mangent une tranche de pain avec du fromage. – They (masculine/mixed) eat a slice of bread with cheese.
Elles mangent une tranche de pain avec du fromage. – They (feminine) eat a slice of bread with cheese.

Notice the verb:

il mange → ils mangent / elles mangent

In pronunciation, mange and mangent sound the same; the difference is only in writing.

Do we need to make any special agreement with pain or fromage because of de or du?

No special agreement is needed beyond singular vs plural of the noun itself.

une tranche de pain – a slice of bread
des tranches de pain – slices of bread
du fromage – some cheese
des fromages – some cheeses / several kinds of cheese

The articles (de, du, des) change to match number and gender, but pain and fromage themselves do not change form unless they become plural (pains, fromages).