vocabulary " friend"

a friend of mine/yours/Billy's etc

best friend (=the friend you like the most) 

good/close friend (=one of the friends you like the most)

old friend (=a friend you have known for a long time)

trusted friend

lifelong friend (=someone who is your friend for the whole of your life)

friend of a friend

 circle of friends (=all the friends someone has)

a mutual friend (=someone who is a friend of both you and someone else)

a childhood/boyhood/girlhood friend

=friend=  buddy = pal = chum = crony  = mate

fair-weather friend=someone who only wants to be your friend when you are successful

Friends of the Earth= FoE an international organization that tries to influence people and governments to protect the environment  false friend = a word in a foreign language that is similar to one in      your  own, so that you wrongly think they both mean the same thing someone who seems to be your friend but is not = 

pen friend =pen pal

someone you write friendly letters to, especially someone in   another country who you have never met