friend has 8 distinct synonyms spread across 4 of its 5 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is foe.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a person you know well and regard with affection and trust
“he was my best friend at the university”
Synonyms, antonyms and the broader and narrower relations for friend come from Princeton University’s WordNet. Full sources and licences.
an associate who provides cooperation or assistance
“he's a good ally in fight”
a person with whom you are acquainted
“I have trouble remembering the names of all my acquaintances”
a person who backs a politician or a team etc.
“all their supporters came out for the game”