A person other than a family member, spouse or lover whose company one enjoys and towards whom one feels affection.

“John and I have been friends ever since we were roommates at college.   Trust is important between friends.   I used to find it hard to make friends when I was shy.”

An associate who provides assistance.

“The Automobile Association is every motorist's friend.   The police is every law-abiding citizen's friend.”

A person with whom one is vaguely or indirectly acquainted.

“a friend of a friend;  I added him as a friend on Facebook, but I hardly know him.”

To act as a friend to, to befriend; to be friendly to, to help.

To add (a person) to a list of friends on a social networking site; to officially designate (someone) as a friend.