Published July 8, 2020 • Updated July 6, 2026 — By French teacher David Issokson, teaching French online since 2014
In French grammar, expressions of cause explain why something happens. This lesson covers useful ways to ask “why”, “how is it that”, and “how can we explain”, beyond basic words like pourquoi (why) and parce que (because). Some expressions are common in everyday French, while others are more formal or literary. Learning them will help you understand written French and give clearer explanations in conversation.
Questions asking how and why
Pourquoi + indicatif
Pourquoi is the most basic and common way to ask “why” in French. It is followed by the indicative when you are asking about a real situation, fact, event or action. The verb can be in the present, passé composé, imperfect, plus-que-parfait, future or another indicative tense.
Pourquoi est-ce qu’elle n’est pas venue ?
Why didn’t she come?
Pourquoi tu apprends le français ?
Why are you learning French?
Pourquoi avez-vous choisi cette école ?
Why did you choose this school?
Comment se fait-il que + subjunctive
Comment se fait-il que means “How is it that…?” or “How come…?” This expression is followed by the subjunctive because it introduces a surprising or questionable situation.
Comment se fait-il qu’il puisse être si arrogant ?
How is it that he can be so arrogant?
Comment se fait-il qu’elle ne soit pas encore arrivée ?
How is it that she still hasn’t arrived?
Comment ça se fait que + subjunctive
Comment ça se fait que also means “How is it that…?” or “How come…?” It is more conversational than comment se fait-il que and is very common in spoken French.
Comment ça se fait que tu n’aies pas compris la question ?
How is it that you didn’t understand the question?
Comment ça se fait qu’il soit déjà parti ?
How come he has already left?
Comment expliquer + noun
Comment expliquer + noun means “How can you explain…?” This structure is used when asking how to explain a specific thing, idea, situation or phenomenon.
Comment expliquer la Sainte-Trinité ?
How can you explain the Holy Trinity?
Comment expliquer ce problème ?
How can you explain this problem?
Comment expliquer que + subjunctive
Comment expliquer que means “How can you explain that…?” It is often followed by the subjunctive when the speaker is reacting to something surprising, strange or difficult to understand.
Comment expliquer qu’il ait refusé cette offre ?
How can you explain that he refused this offer?
Comment expliquer qu’elle soit partie sans rien dire ?
How can you explain that she left without saying anything?
Ways of answering questions
The following expressions are useful for answering questions and giving reasons in French. Some are very common in everyday speech, while others are more formal or literary.
Parce que
Parce que means “because” and is the most common and easiest way to answer a question asking for a reason. Before a vowel or mute h, parce que becomes parce qu’.
Pourquoi est-ce qu’il était en retard ? Parce que sa voiture est tombée en panne.
Why was he late? Because his car broke down.
Je reste à la maison parce qu’il pleut.
I’m staying home because it’s raining.
Puisque
Puisque means “since” or “because”, but it often introduces a reason that is already known, obvious or accepted by both speakers.
Puisqu’il a perdu le pari, il a dû quitter Las Vegas.
Since he lost the bet, he had to leave Las Vegas.
Puisque tu es là, aide-moi !
Since you’re here, help me!
Comme
Comme can mean “like” or “as”. When used to express cause, it means “as” or “since” and usually appears at the beginning of the sentence.
Comme elle était malade, son ami est venu lui rendre visite.
As she was sick, her friend came to visit her.
Comme il pleuvait, nous sommes restés à la maison.
As it was raining, we stayed home.
👉 Comme »
Sous prétexte que
In French, un prétexte is an excuse or pretext. Sous prétexte que translates roughly to “on the pretext that” or “using the excuse that”. It often suggests that the reason given may not be sincere or fully convincing.
Il a raté la réunion sous prétexte qu’il était trop occupé.
He missed the meeting on the pretext that he was too busy.
Elle n’est pas venue sous prétexte qu’elle avait trop de travail.
She didn’t come, using the excuse that she had too much work.
👉 Sous prétexte que »
Vu que, étant donné que, du fait que
Vu que, étant donné que and du fait que all mean “given that” or “since”. Vu que is common in spoken French, while étant donné que and du fait que are more formal.
Vu que le coût de la vie sur la Côte d’Azur est si élevé, beaucoup de gens préfèrent habiter en Espagne.
Given that the cost of living on the French Riviera is so high, many people prefer to live in Spain.
Étant donné qu’il pleut, nous allons reporter la sortie.
Given that it’s raining, we’re going to postpone the outing.
Du fait qu’il travaille beaucoup, il a peu de temps libre.
Due to the fact that he works a lot, he has little free time.
👉 Vu que »
👉 Étant donné que »
👉 Du fait que »
Grâce à
Grâce à means “thanks to” and is usually used for a positive cause. It presents the cause as helpful or beneficial.
Grâce à son français, il a trouvé un bon travail.
Thanks to his French, he found a good job.
Grâce à ton aide, j’ai réussi l’examen.
Thanks to your help, I passed the exam.
À cause de
À cause de means “because of”. It is often used when the cause is negative, unpleasant or responsible for a problem.
À cause de la pluie, nous ne sommes pas venus.
Because of the rain, we didn’t come.
Il est arrivé en retard à cause du trafic.
He arrived late because of the traffic.
Faute de
Faute de means “for lack of” or “due to the lack of”. It is used when something does not happen because there is not enough time, money, experience, evidence or another necessary thing.
Il n’a pas pu trouver de travail faute d’expérience.
He couldn’t find a job due to lack of experience.
Faute de temps, nous n’avons pas terminé le projet.
For lack of time, we didn’t finish the project.
Pour + infinitif passé
Pour + infinitif passé can express the reason someone is rewarded, punished, criticized or blamed. In English, this often translates as “for having done something” or simply “for doing something”.
Il s’est fait arrêter par les gendarmes pour avoir conduit trop vite.
He was stopped by the police for driving too fast.
Elle a été remerciée pour avoir aidé les autres élèves.
She was thanked for helping the other students.
Car
Car means “because”, but it is more formal or literary than parce que. It is common in written French and is often used to explain or justify a statement.
La tondeuse ne marche pas, car elle manque d’essence.
The lawnmower doesn’t work because it is out of gas.
Je ne peux pas venir, car j’ai déjà un rendez-vous.
I can’t come because I already have an appointment.
👉 Car »
En effet
En effet can mean “indeed” or “in fact”. When giving an explanation, it introduces a supporting reason. It is more formal than parce que and often appears after a semicolon, colon or full stop.
La tondeuse ne marche pas ; en effet, elle manque d’essence.
The lawnmower doesn’t work; indeed, it is out of gas.
Il faut partir tôt ; en effet, le train quitte la gare à huit heures.
We have to leave early; in fact, the train leaves the station at eight o’clock.
Common mistake: parce que vs. à cause de
Use parce que before a full clause with a subject and verb.
Je suis en retard parce qu’il y a du trafic.
I’m late because there is traffic.
Use à cause de before a noun, name or pronoun.
Je suis en retard à cause du trafic.
I’m late because of the traffic.
Do not say:
Je suis en retard parce que du trafic.
I’m late because of traffic.
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