We may be on nodding or hand-shaking terms, call each other “friend”, sometimes write to each other with the salutation of “ Dear So-and-So”, etc., etc.
请采纳
People nod their head or shake hands when seeing each other, visit or write to each other when needing help from others, and call each other "pal" or address "Mr. ..." in writing.
When meet nod or shake hands, occupied when visiting or communication, or, colloquially, also say to each other "friend", written or sometimes says "good friend".