Le mot "lundi" est un :

The question asks what the word lundi is. Lundi means Monday, and Monday is a jour de la semaine (day of the week).

The seven days of the week in French are: lundi (Monday), mardi (Tuesday), mercredi (Wednesday), jeudi (Thursday), vendredi (Friday), samedi (Saturday), and dimanche (Sunday).

The other options represent different categories of time or geography:

• pays means country (e.g., la France, le Nigeria)
• mois means month (e.g., janvier, fevrier)
• saison means season (e.g., l'ete, l'hiver)

Note that in French, days of the week are not capitalised unless they begin a sentence.