Learn Hardcore French: Sa sœur préfère les jeans, mais elle lui prête parfois une jupe ou un chapeau. - Her sister prefers jeans, but she sometimes lends her a skirt or a hat.

sœur is a feminine singular noun.
Therefore, you must use sa for “his/her” sister: sa sœur.
son is used before masculine singular nouns (for example, son frère – his/her brother).
ses is for plural nouns, regardless of gender (for example, ses sœurs – his/her sisters).

The owner could be male or female; sa sœur can mean his sister or her sister. Context tells you which one.

Why does it say les jeans and not just jeans without an article, like in English?

In French, you almost always need an article before a noun, even when talking in general.

With verbs of preference (like aimer, préférer, adorer, détester), French normally uses the definite article (le, la, les) to talk about things in general:

Elle préfère les jeans. = She prefers jeans (as a type of clothing, in general).
J’aime le chocolat. = I like chocolate (chocolate in general).

So les jeans corresponds to English “jeans” in general, even though English leaves out the here.

What is the difference between les jeans, des jeans, and le jean?

All three exist, but they do not mean exactly the same thing:

les jeans
- Plural, with definite article.
- Used here after a verb of preference to talk about jeans as a category, generally.
- Sa sœur préfère les jeans. = She prefers jeans (in general, as opposed to skirts, dresses, etc.).
des jeans
- Plural, with indefinite article.
- Means some jeans, an unspecified quantity or number.
- Elle a acheté des jeans. = She bought some jeans.
le jean
- Singular, with definite article.
- Can refer to denim fabric or to jeans as a clothing style seen as a mass noun.
- Elle préfère le jean au tissu classique. = She prefers denim to traditional fabric.

In your sentence, les jeans is chosen because it expresses a general preference.

Why is préfère used instead of something like aime? Is there a grammatical reason?

Grammatically, both aime (likes) and préfère (prefers) can appear here. The choice is mainly about meaning, not grammar.

Sa sœur aime les jeans. = His/her sister likes jeans.
Sa sœur préfère les jeans. = His/her sister prefers jeans (compared to other clothes, like skirts).

Both verbs follow the same article rule (they are verbs of preference, so they take le, la, les before a general noun). The author simply wanted to express preference, not just liking.

What tense is préfère and prête, and what do their infinitives look like?

Both préfère and prête are in the present tense, 3rd person singular (il/elle/on) of regular -er verbs.

Infinitives:
- préférer (to prefer)
- prêter (to lend)

Conjugation in the present (for elle):

elle préfère = she prefers
elle prête = she lends

So Sa sœur préfère… means “His/her sister prefers…” and elle lui prête… means “she lends (to) him/her…” in the present, describing a usual or repeated action.

Why is it elle lui prête and not elle prête lui, like in English word order?

In French, unstressed object pronouns (like me, te, lui, nous, vous, leur, le, la, les) normally go before the conjugated verb in simple tenses:

elle lui prête = she lends to him/her
je lui parle = I speak to him/her
nous leur écrivons = we write to them

You cannot say ✗ elle prête lui; that is ungrammatical in standard French.

The basic pattern is:

Subject + object pronoun(s) + verb
Elle + lui + prête

What exactly does lui mean here, and why not le or la?

The verb prêter works like this:

prêter quelque chose à quelqu’un
(to lend something to someone)

So the person who receives the item is an indirect object (introduced in full form by à).

Full form: Elle prête une jupe à son ami.
With a pronoun: Elle lui prête une jupe.

In the pronoun system:

lui = to him / to her (indirect object, singular)
leur = to them (indirect object, plural)
le / la = him/her/it as a direct object (no preposition à)

So we use lui because:

It stands for à quelqu’un (to someone).
The receiver is an indirect object, not a direct one.

Elle lui prête… = She lends (something) to him / to her.

Who does lui refer to in this sentence? The sister, or someone else?

Grammatically, lui just means to him or to her; it does not tell you who that person is. You need the wider context (earlier sentences) to know.

However, we can say:

Elle in elle lui prête clearly refers back to sa sœur (the sister).
lui is some other person (a friend, brother, etc.), not the sister herself.

If you tried to make lui refer to sa sœur, the meaning would be “She lends a skirt to herself,” which does not fit with lui in normal usage here and would anyway sound strange. So in natural interpretation:

Sa sœur = the subject (she who owns the clothes).
lui = someone else who sometimes borrows them.

Where can I put parfois in this sentence? Is elle lui prête parfois… the only option?

parfois (sometimes) is a fairly flexible adverb. Several positions are possible, with only slight shifts in emphasis:

Sa sœur préfère les jeans, mais elle lui prête parfois une jupe ou un chapeau.
– Neutral and very common; parfois goes after the verb and object pronoun.
Sa sœur préfère les jeans, mais parfois elle lui prête une jupe ou un chapeau.
– Emphasizes “sometimes” a bit more, often used at the beginning of a clause.
Sa sœur préfère les jeans, mais elle prête parfois une jupe ou un chapeau à lui.
– Grammatically possible, but à lui sounds heavy here and is not needed if lui is already before the verb.

The most natural version is the original: elle lui prête parfois….

Why is it une jupe but un chapeau? What decides between une and un?

une and un are the indefinite articles (“a/an”) in French:

une is used with feminine singular nouns.
un is used with masculine singular nouns.

Here:

jupe (skirt) is feminine, so une jupe.
chapeau (hat) is masculine, so un chapeau.

These genders are part of the word’s dictionary entry; you need to learn them with the noun:

une jupe
un chapeau

Why are les jeans plural, but une jupe ou un chapeau are singular?

The difference reflects the type of statement being made:

les jeans is used in a general, category sense:
- Sa sœur préfère les jeans = She prefers jeans as a type of clothing.
une jupe ou un chapeau describes what she actually lends on a particular occasion:
- She usually lends one skirt or one hat at a time (not many at once), so singular makes sense:
  - une jupe = a skirt
  - un chapeau = a hat

So: general preference (plural + definite article) vs. specific objects in concrete actions (singular + indefinite article).

Why is it une jupe ou un chapeau and not une jupe et un chapeau?

Both ou and et are possible grammatically, but they mean different things:

ou = or
- une jupe ou un chapeau suggests that she lends one or the other, not necessarily both at the same time.
et = and
- une jupe et un chapeau would mean she lends a skirt and a hat (both together).

The sentence is describing occasional, limited lending, so ou (“or”) is more natural: sometimes she lends a skirt, sometimes a hat.

Could we say Sa sœur préfère porter des jeans instead of Sa sœur préfère les jeans? Is there a difference?

Yes, you can say that, but there is a nuance:

Sa sœur préfère les jeans.
- Focuses on jeans as a type of clothing that she prefers (compared to other clothes).
Sa sœur préfère porter des jeans.
- Adds the verb porter (to wear).
- Focuses on the action of wearing jeans rather than owning or liking them in the abstract.

Both are correct; the original sentence is slightly more concise and keeps the structure:

préférer + le/la/les + noun to express general preference.