What is the difference between "친절합니다" and "착합니다"?
착하다 good-natured (even by itself)
친절하다 friendly/amicable (to whomever)
다정하다 too kind/sentimental
What does 비열합니다 mean?
It means mean/unkind/nasty
is it always that ?
why could we not put "jeohabnida"
착하다 : good, nice, good-natured, good-hearted
좋다: good, fine, nice
So, depends on the context which nuance you want to convey.
Is it true there is no rule for when to use 가/는 이/은?