Welcome to Expressions bien de chez nous! Today we are doing things a little differently. Instead of starting with the meaning, we are going to let the examples speak first. Because after all, une fois n’est pas coutume. Keep reading and you may already have a good idea of what this expression means before we even explain it.

How and when do you use it?

You are on a diet, but you have allowed yourself a cheat meal at weekends. You have earned it. So on Saturday you decide to treat yourself, and you tell a friend:

“Une fois n’est pas coutume, je vais manger un hamburger ce weekend.”
Just this once, I’m going to have a hamburger this weekend.

By saying this, you are making it clear that this is an exception. You are not abandoning your diet. You are simply allowing yourself a one-off indulgence, and this expression is the perfect way to say so.

Here is a second example, a little closer to home. Imagine you read a new article every week in this series, and one week we send you a message to say there will be nothing this time due to a problem. With this expression, our message would read:

“Pas d’article cette semaine, mais une fois n’est pas coutume.”
No article this week, but it’s just this once.

Have you guessed the meaning? We thought so.

What does it mean?

The key word in this expression is coutume, which means custom or habit. In the context of this phrase, a coutume is not just a personal preference but a regular practice, something done repeatedly over time. We also find une fois, meaning “once”.

Put together in the negative form, une fois n’est pas coutume means that doing something once does not make it a habit. It is the expression you reach for when you are making an exception, stepping outside your usual routine, or allowing yourself something you would not normally do. The implication is always the same: this is a one-off, not a new pattern.

You can use it to justify a treat, to excuse an irregularity, to signal a change of plan, or simply to add a touch of lightness to a situation. It works in professional contexts as much as in everyday conversation.

Where does it come from?

The word coutume dates back to the 12th century, where it designated a way of acting adopted by the majority of people: a collective practice with enough repetition to be considered normal. The idea behind une fois n’est pas coutume is that a single occurrence, by definition, cannot constitute a custom.

The first known written trace of the expression appears in the Institutes Coutumières (1607) by Antoine Loysel, who cites Davot with the sentence: “On ne peut alléguer comme coutume ce qui n’arrive qu’une fois.” In English: you cannot call something a custom if it only happens once. The logic is as clear today as it was in the 17th century.

Keep exploring French expressions

Une fois n’est pas coutume is one of those expressions that feels immediately useful. The moment you learn it, you start finding excuses to say it. Whether you are breaking a diet, skipping a routine or trying something new, it is the perfect phrase to acknowledge the exception without guilt.

Do you have an equivalent expression in your own language? French is full of sayings like this one, rooted in centuries of daily life and common sense. Discover more in our French expressions from Bordeaux series. And if you want to use them in real conversations, our French language courses in Bordeaux are the ideal setting. You can also test yourself with our online quizzes on French expressions.

Come and experience Bordeaux for yourself. Une fois n’est pas coutume, you might just decide to come back every year. Discover the city through our cultural activities in Bordeaux.

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