Saying 'on Monday' and 'every Monday' in French
When you want to talk about your plans for a specific day of the week, English relies on the preposition on. You might say you are going to the movies on Tuesday or resting on Sunday. French handles days of the week quite differently.
In French, you never use a direct translation of on before days of the week such as lundi, mardi, or dimanche. Instead, French uses either the day all by itself or pairs it with the definite article le. The choice depends entirely on whether the event is happening just once or is a regular habit.
For a single, one-off event, you just use the name of the day. You do not need to add any little words before it. If you say mardi, it translates to on Tuesday or this Tuesday, referring to the specific Tuesday coming up.
You will often see words like jeudi and vendredi used exactly this way for making plans or scheduling a meeting. You can also add words like prochain (next) to be even more specific, still without using any article.
When you want to express a recurring habit, like something you do every week, you simply place the definite article le in front of the day. For instance, le samedi translates to on Saturdays or every Saturday.
You can put this time marker at the beginning of your sentence to set the scene, or at the end of the sentence. It works the same way for any day of the week. If you always rest at the end of the week, you use le dimanche, and if you start your routine at the beginning of the week, you use le lundi.
There is one important exception where you use le for a single, one-time occurrence. When you give a complete date that includes the day of the week, the number, and the month, you must use le before the day.
For example, if an appointment is on a specific mercredi, the full date format requires the article to single out that exact day on the calendar.
Remember that French ignores the word on for days of the week. Use the day alone for a single upcoming event, and add le when you want to describe a routine that happens every week. The only time you use le for a single event is when you are stating a full calendar date.