La contrôleuse nous dit de changer de voie, parce que le train pour Paris part plus tôt.

Contrôleuse is the feminine form of contrôleur. It means the person is female.

• le contrôleur = a male ticket inspector / conductor
• la contrôleuse = a female ticket inspector / conductor

French job nouns often change form depending on gender. Here, la also tells you the noun is feminine.

Here, nous means to us, not we.

In La contrôleuse nous dit..., the pronoun nous is an indirect object:

• elle dit à nous → in normal French, this becomes elle nous dit

So the structure is:

• La contrôleuse = the subject
• nous = to us
• dit = says / tells

That is why the sentence means the inspector is telling us something.

After dire when you tell someone to do something, French normally uses:

dire à quelqu’un de + infinitive

Example:

• Elle dit à Paul de venir.
• Elle nous dit de changer de voie.

In your sentence, à nous becomes the pronoun nous, so you no longer see à separately:

• La contrôleuse dit à nous de changer → not said this way
• La contrôleuse nous dit de changer → correct

So:

• nous = to us
• de changer = to change

This is a very common pattern in French.

With changer de + noun, French often means change what kind of thing you are using / switch to another one, and it usually does not use an article.

So:

• changer de voie = change tracks / switch platforms or lines, depending on context
• changer de train = change trains
• changer de place = change seats
• changer d’avis = change one’s mind

If you said changer de la voie, it would sound unusual here. The article is normally omitted in this pattern.

Voie has several meanings depending on context, but in train or station language it often means something like:

• track
• platform line
• sometimes more generally route or line

So changer de voie means moving to a different track or platform area for the correct train.

A learner may notice that voie is also used in other contexts:

• voie ferrée = railway track
• voie rapide = fast lane / expressway lane
• la voix with an x means voice, which sounds the same but is a different word

Because pour shows destination: the train is for / to Paris.

• le train pour Paris = the train going to Paris

Using à Paris would usually describe location, not destination:

• un train à Paris = a train in Paris

So if you want to say where the train is headed, pour is the natural choice here.

French often uses the present tense for scheduled future events, just like English can.

• Le train part plus tôt.
• The train leaves earlier.

This is especially common with:

• trains
• flights
• timetables
• appointments
• planned events

So even though the departure happens later, the present tense is perfectly normal because it is a scheduled fact.

Plus tôt means earlier or sooner.

In this sentence, it means the train for Paris leaves earlier than expected, or earlier than another train/time.

Compare:

• plus tôt = earlier
• plus tard = later

Be careful not to confuse tôt with tout:

• tôt = early
• tout = all / everything / very, depending on context

So:

• il part tôt = it leaves early
• il part plus tôt = it leaves earlier

The comma is there because the sentence has two parts:

• La contrôleuse nous dit de changer de voie
• parce que le train pour Paris part plus tôt

The second part gives the reason. In French, a comma before parce que is often used when the sentence is a bit longer or when the writer wants a clear pause. It is not unusual here.

You may also see sentences without the comma in other contexts:

• Je pars parce qu’il est tard.

So the comma here is mainly about clarity and rhythm, not a different grammar rule.

Dit is the third-person singular present form of dire.

Present tense of dire:

• je dis
• tu dis
• il / elle / on dit
• nous disons
• vous dites
• ils / elles disent

So La contrôleuse nous dit... means The inspector tells us... or is telling us...

This verb is irregular, so it is worth memorizing its forms.