une goutte de pluie
baisse if you mean (rain) drop. Tomber if you mean to drop (something)
In Serbian rain drop is kap kiše
Drop off
according to http://translate.reference.com, there is no translation from English "raining" to french. Rain in french is pluie so, find a different way to say raining in french. Say: "My, look at all that rain" instead of "It's raining".
If you want to say it is raining, it is "Il pleut". If you want to say rain then it is pluie.
The puddle said to the rain, "Please stop! I'm already full!"
j'aime la pluie
if you mean why does rain drop , it is because of gravity
Un impermeable ( often just 'imper' )
Vous jouez sous la pluie.
Je n'aime pas la pluie
La pluie est arrivée.