Quand elle parle de son enfance, Marie a une larme à l’œil.

Because parle is the conjugated verb form that matches elle.

• Infinitive: parler = to speak / to talk
• With elle in the present tense: elle parle = she speaks / she talks

So in Quand elle parle..., the verb has to be conjugated.

It can feel like either, depending on context.

In this sentence, because the verb is in the present tense and the statement sounds general, quand often has the sense of when(ever):

• Quand elle parle de son enfance... = When / Whenever she talks about her childhood...

If the speaker is describing a repeated or typical reaction, whenever is a very natural way to understand it.

Because parler usually takes de when you say what someone is talking about.

• parler de quelque chose = to talk about something
• parler à quelqu’un = to speak to someone

So:

• elle parle de son enfance = she talks about her childhood

The de is required by the verb pattern here.

This is a very common question.

Normally, since enfance is feminine, you would expect sa. But French uses mon, ton, and son before a feminine noun that begins with a vowel or a mute h.

That is done for smoother pronunciation.

So:

• sa maison
• but son enfance

Even though enfance is feminine, son is correct here because enfance starts with a vowel.

Yes. son can mean his or her.

In French, possessive adjectives agree with the thing possessed, not with the owner.

Here, the possessed thing is enfance, and the owner is understood from context to be Marie. So son enfance means her childhood.

This is different from English, where his and her depend directly on the person.

It can sound a little unusual to an English speaker, but it is possible in French.

Here, elle refers to Marie, and the sentence identifies her in the main clause:

• Quand elle parle de son enfance, Marie...

French can allow this kind of structure when the reference is clear enough. Still, a learner might find these versions more straightforward:

• Quand Marie parle de son enfance, elle a une larme à l’œil.
• Marie a une larme à l’œil quand elle parle de son enfance.

So the original sentence is understandable and natural enough, but not the only way to say it.

Because French often uses the definite article with body parts when the owner is already obvious.

So instead of saying her eye, French often says simply the eye:

• à l’œil = literally at the eye / in the eye
• understood here as in her eye

This is very common in French:

• j’ai mal à la tête = my head hurts
• il se lave les mains = he washes his hands

So une larme à l’œil is the normal phrasing.

It suggests that someone is emotional and has a tear in their eye, or is close to crying.

It does not necessarily mean full-on crying. It often implies a softer, more restrained emotion, such as being moved by a memory.

A very similar expression is:

• avoir les larmes aux yeux = to have tears in one’s eyes

That version can sound slightly stronger or more general.

Because the expression focuses on a single tear and the idea of it appearing in one eye.

So une larme à l’œil is a fixed, natural expression.

French could also use a plural expression in a slightly different way:

• les larmes aux yeux = tears in the eyes

Both are natural, but they do not sound exactly the same. The singular version can feel a bit more specific and delicate.

Because Quand elle parle de son enfance is an introductory clause, and the main clause comes after it:

• Quand elle parle de son enfance, Marie a une larme à l’œil.

The comma helps separate the time clause from the main statement. This is similar to English punctuation with an introductory clause.

Œil is an irregular-looking word, and many learners find it tricky.

Its pronunciation is approximately uhl-y compressed into one syllable, or in IPA /œj/.

A few useful points:

• l’œil is pronounced with the l attached at the start
• the plural is irregular: yeux

So:

• l’œil = the eye
• les yeux = the eyes

That singular/plural pair is one of the classic irregular noun forms in French.