Ma sœur retourne chez l’opticien parce que ses anciennes lunettes sont trop lourdes.

French possessive adjectives agree with the gender and number of the noun being possessed, not with the owner.

• sœur is a feminine singular noun
• so the correct form is ma sœur

You use:

• mon with masculine singular nouns: mon frère
• ma with feminine singular nouns: ma sœur
• mes with plural nouns: mes sœurs

One extra point: before a feminine noun starting with a vowel sound, French often uses mon instead of ma for ease of pronunciation, as in mon amie. But sœur does not start with a vowel sound, so ma sœur is correct.

Retourne comes from retourner, which here means to go back or to return to a place.

So Ma sœur retourne chez l’opticien means that she is going back to the optician.

French often distinguishes between:

• retourner = to go back
• revenir = to come back

The difference is similar to English go back versus come back. In this sentence, the focus is on her going back to that place, so retourne is natural.

Chez is used to mean to/at the home, business, office, or place of a person.

So:

• chez le médecin = at/to the doctor’s
• chez le boulanger = at/to the baker’s
• chez l’opticien = at/to the optician’s

Even though the optician may work in a shop, French still often uses chez because the idea is at that person’s place/business.

Using à l’opticien would sound unnatural in this context.

Because opticien begins with a vowel, le contracts to l’ in front of it.

So:

• le + opticien → l’opticien

This is very common in French:

• l’homme
• l’école
• l’ami

The apostrophe shows that a vowel has been dropped.

Not exactly.

An opticien is usually the person or shop that deals with glasses, frames, and lenses. In many contexts, optician is the best English translation.

Depending on the country and context:

• opticien = optician
• ophtalmologiste = ophthalmologist / eye specialist
• optométriste = optometrist (where that profession exists distinctly)

In this sentence, because the problem is with glasses, opticien makes perfect sense.

Because lunettes is plural, so the possessive adjective must also be plural.

French possessives agree with the thing possessed:

• son / sa / ses = his, her, its
• ses is used with plural nouns

So:

• sa lunette = his/her glasses lens or single item
• ses lunettes = his/her glasses

Here lunettes is plural, so ses is required.

It can mean her, his, or sometimes its. French does not choose the possessive based on the owner’s gender. It chooses it based on the gender and number of the noun possessed.

So:

• ses lunettes can mean her glasses or his glasses

In this sentence, because the subject is ma sœur, we understand that ses anciennes lunettes means her old glasses.

Normally, lunettes is used in the plural when talking about a pair of glasses.

So:

• des lunettes = glasses
• mes lunettes = my glasses

This works much like English glasses. There is a singular noun lunette, but it usually does not mean a normal pair of eyeglasses in everyday use.

Because the noun is plural, the adjective must also be plural:

• anciennes
• lourdes

Because adjectives in French usually agree with the noun they describe in gender and number.

Here the noun is:

• lunettes = feminine plural

So the adjective ancien must become feminine plural:

• masculine singular: ancien
• feminine singular: ancienne
• masculine plural: anciens
• feminine plural: anciennes

That is why the sentence has ses anciennes lunettes.

For the same reason: adjective agreement.

The adjective lourdes describes lunettes, which is feminine plural, so the adjective must also be feminine plural.

Forms of lourd:

• lourd = masculine singular
• lourde = feminine singular
• lourds = masculine plural
• lourdes = feminine plural

So:

• des sacs lourds = heavy bags
• des lunettes lourdes = heavy glasses

Not quite. Trop usually means too, in the sense of more than is acceptable or comfortable.

So:

• très lourdes = very heavy
• trop lourdes = too heavy

In this sentence, the idea is that the glasses are uncomfortably heavy, which explains why she is going back to the optician.

Parce que means because and introduces the reason.

The sentence structure is:

• Ma sœur retourne chez l’opticien = main statement
• parce que ses anciennes lunettes sont trop lourdes = reason

So the second part explains why she is going back.

French learners sometimes confuse:

• parce que = because
• pourquoi = why
• car = because/since, often more formal or written

In everyday French, parce que is extremely common.

Because the subject of that clause is ses anciennes lunettes, which is plural.

The verb être must agree with its subject:

• elle est
• les lunettes sont

So:

• ses anciennes lunettes sont trop lourdes

Even though glasses refers to one pair, the noun is grammatically plural, so the verb is plural too.

It can mean both, depending on position and context.

With many adjectives, position changes meaning:

• une ancienne maison often means an old house
• mon ancien professeur often means my former teacher

In this sentence, anciennes lunettes most naturally means old glasses—the pair she had before or the pair she has been using.

Because the context is about replacing or adjusting glasses, English old glasses is the natural understanding.

It follows a very common French pattern:

• subject: ses anciennes lunettes
• verb: sont
• adjective phrase: trop lourdes

So literally:

• her old glasses
  • are
    • too heavy

The adjective comes after the verb here because it is part of the predicate, just like in English:

• The glasses are heavy
• Les lunettes sont lourdes

That is completely standard.

A helpful way to break it up is:

• Ma sœur retourne chez l’opticien
• parce que ses anciennes lunettes
• sont trop lourdes

This helps you hear the structure:

1. who is acting: Ma sœur
2. what she is doing: retourne chez l’opticien
3. why: parce que...
4. explanation: ses anciennes lunettes sont trop lourdes

That chunking can make the sentence easier to understand and say naturally.