Paul était en retard, mais sa sœur a fini par lui pardonner.

Était is the imparfait form of être.

In this sentence, Paul était en retard describes a state or background situation in the past: Paul was late. French often uses the imparfait for descriptions, ongoing situations, and context.

If you said a été en retard, it would sound more like a completed event viewed as a whole: he was late / he ended up being late in a more punctual, bounded sense. Here, était is the more natural choice because being late is the situation that sets up the rest of the sentence.

En retard means late.

It is a fixed expression used with être:

• être en retard = to be late

Examples:

• Je suis en retard. = I’m late.
• Nous étions en retard. = We were late.

French uses en retard, not just retard by itself after être.

Because être en retard is the normal French expression.

French often uses prepositions in places where English does not. So although English says to be late, French says literally something closer to to be in lateness/delay.

You should learn en retard as one whole chunk:

• être en retard
• arriver en retard = to arrive late

Because sœur is a feminine singular noun, and French possessive adjectives agree with the thing possessed, not with the owner.

So:

• son frère = his/her brother
• sa sœur = his/her sister

The fact that the sister belongs to Paul does not matter for the form. What matters is that sœur is feminine singular, so we use sa.

Grammatically, sa can mean either his or her.

French possessive adjectives do not show the gender of the owner. They show the gender and number of the noun that follows.

So:

• sa sœur can mean his sister or her sister
• here, because of the context with Paul, it means his sister

Finir par + infinitive means to end up ..., to finally ..., or to eventually ...

So:

• sa sœur a fini par lui pardonner = his sister eventually forgave him / ended up forgiving him

This expression suggests that it may have taken time, hesitation, or difficulty before the action happened.

It is more expressive than simply saying sa sœur lui a pardonné.

A fini is the passé composé, which presents the action as a completed event.

Here, the completed event is that the sister eventually did forgive him.

Using finissait would be the imparfait, which would sound unfinished, habitual, or descriptive. That does not fit as well here, because the sentence focuses on the result: she forgave him in the end.

So the contrast is:

• Paul était en retard → background state
• sa sœur a fini par lui pardonner → completed result

Because with pardonner, the person being forgiven is normally an indirect object in French.

So:

• pardonner à quelqu’un = to forgive someone
• lui pardonner = to forgive him/her

That is why French uses lui, not le.

Compare:

• Je lui pardonne. = I forgive him/her.
• Je le vois. = I see him.

The verb patterns are different:

• voir quelqu’un → direct object
• pardonner à quelqu’un → indirect object

Yes. Pardonner can take a direct object for the thing forgiven, and an indirect object for the person.

For example:

• Je pardonne cette erreur à Paul. = I forgive Paul for this mistake.

Here:

• cette erreur is the direct object
• à Paul is the indirect object

So in lui pardonner, the pronoun refers to the person forgiven.

Because object pronouns in French usually come before the verb they belong to.

Here, lui belongs to pardonner, which is in the infinitive:

• a fini par lui pardonner

So the pronoun goes right before pardonner.

Compare:

• Elle lui pardonne.
• Elle va lui pardonner.
• Elle a fini par lui pardonner.

In each case, lui sits in front of the verb it is linked to.

In finir par + infinitive, par is simply part of the fixed expression.

You do not translate it word for word as by in a literal way here. Instead, learn the whole structure:

• finir par faire quelque chose = to end up doing something

Examples:

• Il a fini par comprendre. = He eventually understood.
• Nous avons fini par accepter. = We ended up accepting.

Because mais means but and connects two clauses:

• Paul était en retard
• sa sœur a fini par lui pardonner

The comma helps separate the two ideas clearly. In French, as in English, a comma before mais is very common when it links two full clauses.

Sœur is pronounced roughly like a single-syllable sound similar to the vowel in French heure.

The œ is a French ligature, and in sœur it represents a vowel sound that does not exist exactly in English. A close approximation for English speakers is something like sur said with rounded lips, but it is best learned by listening.

A few related words:

• sœur = sister
• cœur = heart
• œuf = egg

Yes, that is grammatically correct.

But the meaning is slightly different:

• sa sœur lui a pardonné = his sister forgave him
• sa sœur a fini par lui pardonner = his sister eventually forgave him / ended up forgiving him

The version with a fini par adds the idea that forgiveness came in the end, perhaps after some reluctance or delay.

Yes. It is a very typical pattern.

French often uses:

• imparfait for the background or ongoing situation
• passé composé for the main event or result

So here:

• Paul était en retard → background state
• mais sa sœur a fini par lui pardonner → event/result

This contrast is one of the most important things for English speakers to get used to in French past narration.