absorbing or controlling possession of the mind by any interest or pursuit; lively interest

He shows marked enthusiasm for his studies.

an occupation, activity, or pursuit in which such interest is shown

Hunting is his latest enthusiasm.

any of various forms of extreme religious devotion, usually associated with intense emotionalism and a break with orthodoxy.

noun

aloofness , apathy , coldness , coolness , doubt , indifference , lethargy , pessimism , weariness , calmness , caution , lukewarmness , wariness

noun

activity , ardency , ardor , avidity , conviction , craze , dash , devotion , eagerness , earnestness , ecstasy , lan , emotion , energy , exhilaration , fad , fanaticism , feeling , fervor , fever , fieriness , fire , flame , flare , frenzy , fury , gaiety , glow , go * , heat , hilarity , hobby , impetuosity , intensity , interest , joy , joyfulness , keenness , life , mania , mirth , nerve , oomph * , orgasm , passion , pep , rapture , red heat * , relish , snap , spirit , transport , vehemence , verve , vim , vivacity , warmth , zeal , zealousness , zest , rage , ebullience , ebulliency , empressement , esprit , euphoria , excitement , exuberance , fervency , gusto , kindle , love , lyricism , unction , vigor