na-adjective
Describes a person, attitude, relationship, or atmosphere that is warm and cooperative.
彼はいつも友好的な態度で接してくれる。
He always treats me in a friendly manner.
会議は友好的な雰
The meeting was held in a friendly atmosphere.
仲良し is a more casual, personal term for being on good terms, often used between friends or children.
Compound of 友好 (friendship) + 的 (-like, -ish). The suffix 的 forms adjectival nouns from Sino-Japanese nouns.