This is the 6973rd most frequent French word.
majeur
"Major" or "adult; of legal age."
Here, 'majeur' is used to indicate that the problem is the most significant one among others.
Le problème majeur est le manque de ressources.
The major problem is the lack of resources.
Here, 'majeur' is used as an adjective to describe the importance of someone's role.
Son rôle dans ce projet est majeur.
His role in this project is significant.
In this sentence, 'majeur' refers to the legal age when someone becomes considered an adult.