Au vestiaire, je retrouve mon cartable près de celui de mon copain.

Because au is the mandatory contraction of à + le in French.

• à le vestiaire → au vestiaire
• This is just like:
  • au parc = à le parc
  • au cinéma = à le cinéma

So au vestiaire literally comes from à le vestiaire, but French always contracts it.

Vestiaire usually means a place where coats, bags, or clothes are left. Depending on context, it can mean:

• cloakroom
• locker area
• changing room
• coat check

In a school context, it often suggests the place where students leave their things before class or sports.

This opening phrase sets the scene: it tells you where the action happens.

French often puts a place expression at the beginning of the sentence for context:

• Au vestiaire, je retrouve...
• À l’école, je vois mes amis.
• Dans la cour, les enfants jouent.

In English, this is similar to saying In the cloakroom, I find... or At the locker area, I find...

Retrouver usually means to find again, to get back, or to come across again.

So:

• je trouve = I find
• je retrouve = I find again / I recover / I get back

In this sentence, je retrouve mon cartable suggests that the speaker is finding their schoolbag again, probably after leaving it somewhere.

French often uses a possessive adjective like mon, ton, son, etc. when talking about personal belongings.

So:

• mon cartable = my schoolbag
• le cartable = the schoolbag

Here, mon cartable is natural because the speaker is talking about their own bag.

Cartable usually means a schoolbag or school satchel, especially for a student.

It is more specific than a general word like sac.

• un sac = a bag
• un cartable = a schoolbag / satchel

So the sentence sounds like something a student would say.

Près de is a fixed expression meaning near or close to.

You have to learn it as a whole unit:

• près de la porte = near the door
• près du mur = near the wall
• près de celui de mon copain = near my friend’s one

The de is simply part of the expression près de. You cannot leave it out.

Celui means the one. It replaces a masculine singular noun that has already been mentioned or is understood from context.

Here, celui stands for cartable.

So:

• mon cartable près de celui de mon copain
• = my schoolbag near my friend’s one
• more natural English: my schoolbag near my friend’s

French uses celui to avoid repeating cartable.

French often avoids repetition by using demonstrative pronouns like:

• celui = the one
• celle = the one, feminine
• ceux = the ones, masculine plural
• celles = the ones, feminine plural

So instead of saying:

• mon cartable près du cartable de mon copain

French prefers the smoother:

• mon cartable près de celui de mon copain

This is very natural and common.

Because celui refers to cartable, and cartable is masculine.

• un cartable → masculine
• so the matching pronoun is celui

If the noun were feminine, you would use celle instead:

• ma veste près de celle de mon copain
• = my jacket near my friend’s

They do two different jobs:

• près de = near
• celui de mon copain = the one of my friend / my friend’s one

So the structure is:

• près de
  • celui de mon copain

The first de belongs to près de. The second de shows possession or relationship: the one belonging to my friend.

Copain often means friend, but it can sound a little more informal than ami. It can also mean mate or buddy depending on context.

Very roughly:

• ami = friend
• copain = friend / buddy / mate

In everyday speech, mon copain can also mean my boyfriend, but here that meaning is unlikely because the context is about a schoolbag in the cloakroom. So here it simply means my friend.

It is not always absolutely required, but it is very natural when a sentence begins with a setting phrase like this.

The comma helps separate the context from the main action:

• Au vestiaire, je retrouve mon cartable...

Without the comma, the sentence is still understandable, but the comma makes the structure clearer and more natural in writing.

A very literal breakdown would be:

• Au vestiaire = In the cloakroom / At the locker area
• je retrouve = I find again / I get back
• mon cartable = my schoolbag
• près de = near
• celui = the one
• de mon copain = of my friend / belonging to my friend

So literally:

In the cloakroom, I find my schoolbag again near the one belonging to my friend.

Natural English would usually be:

In the cloakroom, I find my schoolbag near my friend’s.