First, for future reference, it will help you and others to understand and help you better if you provide the context and sentences you saw a word in. Okay here it is : 친해 comes from 친하다, an adjective ("descriptive verb") meaning "to be close (to)". It is commonly seen in the phrase "친하게 지내요". "Another way to say "Let's be friends" as a greeting when first talking to someone/introducing yourself/getting to know them is 친하게 지내요" quoting myself from another notebook here. Haha 친해하다 is incorrect. Examples : 친한 친구 - a close friend, a buddy 앞으로 친하게 지냅시다 - Let's be good friends from now on. 나는 마크와 매우 친하다 - I'm good friends with Mark./I'm really close to Mark./Mark and I are very close./I'm really close friends with Mark. :) I hope I could help.