Is "pline" for people (as in "I can't eat more, I'm full") or for any kind of container (as in "the bottle is full")? Or even both?
How are you supposed to know if its saying "i" or "they" when sunt is the same conjugation used for both?
Sunt plin. -> Eu sunt plin. (I am full.)
Sunt plini. -> Ei sunt plini. (They are full.)
Think about French 'plein' and Latin 'plenus'.
That doesn't help when you don't speak French or Latin