Introduction.

obsession
əbˈsɛʃ(ə)n/
noun
the state of being obsessed with someone or something.
an idea or thought that continually preoccupies or intrudes on a person's mind.
plural noun: obsessions

synonyms: fixation, ruling/consuming passion, passion, mania, idée fixe, compulsion, preoccupation, enthusiasm, infatuation, addiction, fetish, craze, hobby horse.