An ardent fan is someone who is extremely passionate and devoted to a particular person, team, or cause. A FIEND is a person who is obsessed with something, while a DEVOTEE is someone who is devoted to a particular cause or person. An ADMIRER is someone who has great respect and admiration for someone or something, while a LOVER is someone who has strong feelings of love and affection. A BOOSTER is someone who actively supports and promotes something, and an IDOLIZER is someone who admires and adores someone or something. All of these terms can be used to describe an ardent fan.