plein
full
filled
crowded/packed
Le bus est déjà plein, on va devoir attendre le prochain.
The bus is already full; we'll have to wait for the next one.
a lot of
many
lots of
J'ai plein de trucs à te dire sur ce qui s'est passé hier.
I have a lot of things to tell you about what happened yesterday.
the act or result of filling (esp. filling a vehicle's tank); a full tank
J'ai fait le plein avant de partir en vacances.
I filled up (the tank) before leaving on vacation.
Notes
GENERAL INFO
Plein means "full" (adjective) or "very/lots of" (adverb). As an adjective, it agrees in gender and number (plein, pleine, pleins, pleines).
USAGE
As an adjective: "Le verre est plein." (The glass is full.) "La salle est pleine." (The room is full.)
As an adverb (often informal): "J'ai plein de choses à faire." (I have lots of things to do.)
TRAPS
Remember plein agrees as an adjective ("une assiette pleine"). "Plein de" is an informal equivalent to "beaucoup de" (a lot of).
"En plein" means "in the middle of" or "right in."
To know if "plein" is an adjective or adverb, try replacing it by "rempli". If you can, then it's an adjective and if not, it's an adverb and will not agree.
