With because, since and as, the sentence indicates the reason for a fact. Because directly answers the question “why?” and is often followed by the main clause: subject + verb + effect, then because + cause. Since presents a reason already known or obvious to the interlocutor. As often places the cause at the beginning of the sentence: as + cause, then subject + verb + effect. In everyday life, we say: I stay home because it’s raining. Since it is late, we are leaving. As it was cold, I closed the window. These constructions naturally link two ideas, as in Causal Conjunctions.

Common ways to express the cause

Usage	Explanation
Direct cause	We use parce que to give the simplest and most frequent reason.
Cause already known	We use puisque when the cause is presented as obvious to the person listening.
Cause at the beginning of the sentence	We use comme at the start of the sentence to announce the cause before the result.

When the cause is negative, one uses à cause de + noun or noun phrase. The construction presents an troublesome, unpleasant or annoying result: The train was late because of the snow. When the cause yields a favorable result, one uses grâce à + noun or noun phrase: We finished early thanks to his help. Both expressions introduce an external cause, but the judgement changes. À cause de marks an obstacle, a loss, a difficulty. Grâce à marks an advantage, a success, a progress. With a person’s name, grâce à values their action, while à cause de makes them responsible for a problem.

Choice between negative and positive cause

Idea
We use à cause de for a cause that produces an unpleasant or bothersome effect.
We use grâce à for a cause that yields a positive or useful effect.

En raison de + noun appears mostly in a more formal register, often in official, administrative or journalistic texts: The match was cancelled due to the rain. This construction stays close to the neutral cause and is suitable when you want to explain a fact without emotional emphasis. Par appears in certain well-established cause expressions: par peur, par erreur, par curiosité, par manque de temps. It is also used to indicate the means in other contexts, but here it presents the motive that prompts action. The choice depends on style and the expression used. For place and time prepositions, see Prepositions of Place and Prepositions of Time.

Formal uses of the cause

Usage	Explanation
Formal register	We use en raison de in a more formal style to announce a cause or motive.
Cause in a fixed construction	We use par in certain expressions of cause to mark an origin or trigger.

Pour expresses the goal sought. With a noun, the structure is: pour + noun. It designates the use or the destination of an action: I bought this book for the trip. With an infinitive, the structure is: pour + infinitive. It shows the intention of a subject acting in order to achieve a result: I work to save money. The subject of the main action and the subject of the infinitive are the same. This construction is used to announce a simple, concrete and immediate objective, without developing a full subordinate clause.

Use of for for the goal

Idea
We use pour followed by a noun to indicate the objective of an action.
We use pour followed by an infinitive to express an intention or a goal.

Afin de + infinitive expresses the goal with the same subject in the two actions: He closes the door in order to keep the heat. The construction is more formal than pour + infinitive. Pour que introduces a subordinate clause and therefore requires a conjugated verb: He closes the door so that the heat stays inside. Here, the subject of the main clause and the subject of the subordinate clause can be different. With afin de, the construction remains compact. With pour que, the goal is developed in a full sentence. This difference often appears in structures studied with Conjunctions of Subordination.

Two ways to express the goal

Idea
We use afin de followed by an infinitive to express a goal in a more polished way.
We use pour que followed by a verb in the subjunctive to express a goal with a different subject.

De peur de + infinitive expresses fear of an outcome: the subject acts to avoid something. She speaks softly for fear of waking the baby. The goal is not pursued for itself, but to prevent a dreaded effect. Sous prétexte de + noun or infinitive presents a given motive as an excuse, often with a sense of doubt, hypocrisy or an unconvincing pretext: He left under the pretext of tiredness. Sous prétexte de signals that the stated reason is not necessarily the real one. The first construction shows fear; the second shows a dubious justification.

de peur desous prétexte de

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Cette tournure présente une excuse douteuse ou un motif qui cache souvent une autre intentionCette tournure exprime la crainte d un résultat que l on veut éviter

Expressions of fear and excuse

Word	Definition
de peur de	This construction expresses the fear of an outcome that we want to avoid.
sous prétexte de	This construction presents a dubious excuse or a motive that often hides another intention.

Scramble

The cause explains why something exists or happens. The purpose explains what a person seeks to obtain. Compare: He stays home because he is sick. Here, the illness is the real cause. He stays home to rest. Here, rest is the intended goal. With the cause, the action follows from a fact already present. With the goal, the action is oriented toward a future result. The same event can sometimes be phrased in both ways, but the perspective changes: He spoke aloud because of the noise describes a suffered reason; He spoke loudly to cover the noise describes an intention.

Distinguishing the real cause and the goal

Idea
We choose a cause construction when the sentence explains why something already happens.
We choose a goal construction when the sentence indicates a sought objective.
We choose an intention construction when the speaker states what he wants to obtain.

The cause or purpose complement often comes after the verb, especially when it explains the main action: We leave early to avoid traffic. It can also be placed at the beginning of the sentence to foreground the reason: Because of the strike, the office is closed. When the complement is long, the sentence flows better if it is placed after the main clause. When it is short and you want to emphasize it, it is often placed at the beginning. In a simple sentence, the natural order remains subject + verb + complement, then the cause or goal adds to the information.

Natural position of complements of cause and purpose

Idea
The cause complement often goes after the verb to keep the sentence smooth.
The purpose complement often goes at the end of the sentence when it completes the action.
You can move the complement to the beginning of the sentence to highlight the cause.