A fetish is a very specific preference in sex: a specific idea, object, context or act that causes a person to experience sexual arousal or orgasm.

In the more strict sense of the term, a fetish is something without which a person cannot become aroused or orgasm. (For example, if someone with a foot fetish will only orgasm when touched by feet or when seeing feet.)

In the more lax sense of the term, a fetish is just something that a person really likes in a sexual context. (For example, someone is really turned on by redheads, but can have sex and orgasm without a redheaded partner, it’s just that a redhead is an additional bonus and a heightened experience.)