The term fan characterises one who has an intense, occasionally overwhelming and often irrational/uncritical admiration or like of a person, work of art, idea, or trend. The word probably derives from the adjective fanatical.

Fans collectively may, especially if expressing interest in some organised or consistent manner, coalesce into fandom, or be known as a fanbase, particularly when they are fans of music groups. Non-sports fans sometimes self-address as the fen.

In a few cases, fans may become so obsessed with the (presumably human) objects of their infatuation that they become stalkers.

The fan (aficionado) should remain distinct from the air-movement device.