Learn Hardcore French: Paul prend son sac, et Marie prend le sien. - Paul takes his bag, and Marie takes hers.

It can mean either; the form depends on the noun’s gender/number, not the owner’s gender. In the first clause the owner is Paul, so it’s “his bag.” If the subject were Marie, son sac would mean “her bag.”

To avoid ambiguity, French sometimes adds à lui / à elle: son sac à lui, son sac à elle.

Why do we switch to le sien instead of repeating son sac?

Le sien is the possessive pronoun that replaces a known noun plus its possessive (here, it stands for son sac). It avoids repetition: Paul prend son sac, et Marie prend le sien = “…and Marie takes hers.”

What is the le doing in le sien?

French possessive pronouns take a definite article that agrees with the thing owned:

le sien (masculine singular)
la sienne (feminine singular)
les siens (masculine plural)
les siennes (feminine plural)

Here, sac is masculine singular, so it’s le sien.

Does sien agree with the owner (Marie), or with the noun?

With the noun. Sien/sienne/siens/siennes agree in gender and number with the thing possessed, not with who owns it. So even for Marie (female), if the item is masculine singular (sac), you use le sien.

Could it be la sienne?

Only if the replaced noun were feminine. For example: Paul prend sa valise; Marie prend la sienne (“valise” is feminine). With sac (masculine), it must be le sien.

How do we know le sien refers to Marie’s bag and not Paul’s?

By default, a third‑person possessive pronoun like le sien refers to the subject of its own clause. In Marie prend le sien, the subject is Marie, so it means “her bag.” If you wanted “Marie takes Paul’s bag,” you’d say Marie prend le sac de Paul (not le sien).

Can I say le sac de Marie instead of le sien?

Yes: Paul prend son sac, et Marie prend le sac de Marie is grammatical but heavy and repetitive. Le sien is the natural, concise choice once the noun is known.

Why is there a comma before et? Is it necessary?

It’s optional. Standard French usually omits the comma before et joining two clauses: Paul prend son sac et Marie prend le sien. A comma can be used for rhythm or clarity, but you generally don’t need it here.

Why is it prend in both clauses and not prennent?

Each clause has its own singular subject (Paul, Marie), so each takes prend (3rd person singular). You’d use prennent only if the subject were plural within one clause, e.g., Paul et Marie prennent…

Could I say Paul et Marie prennent leur sac instead? What would that mean?

…leur sac (singular) usually implies one bag shared by both.
…leurs sacs (plural) means each takes their own bag(s). Your original sentence makes it explicit that each person takes their own, using son sac and le sien.

Can I drop the second prend and say Paul prend son sac, et Marie le sien?

In careful, neutral French you repeat the verb: …et Marie prend le sien. Elliptical versions like Paul prend son sac; Marie, le sien exist in literary or very concise styles, but they’re best avoided by learners in everyday writing.

How would the forms change with different nouns?

Feminine singular noun: Paul prend sa voiture; Marie prend la sienne.
Plural masculine noun: Paul prend ses livres; Marie prend les siens.
Plural feminine noun: Paul prend ses affaires; Marie prend les siennes.

Any quick pronunciation tips?

prend: roughly “prahn” (nasal n; final d silent)
son: “sohn” (nasal)
sac: “sak”
le sien: “luh syen” with a nasal ending on “sien”

When would I use prendre versus apporter/emporter?

prendre: “to take” (pick up, grab). Paul prend son sac = he picks it up/takes it.
emporter: to take something away with you (from here to elsewhere).
apporter: to bring something to a place/person (toward here or a destination). In many everyday contexts, prendre is fine when you mean “pick up/grab your bag.”