ネツ 
あつ.い 
() heat () fever () passion
            
ねつ (n,n-suf) fever, temperature
あつあつ (adj-na,n,adj-no) (1) piping hot, (2) passionately in love
あつい (adj-i) hot (thing)
ねっする (vs-s) to heat, to heat up
ねつい (n) zeal, enthusiasm
ねっき (n) heat, hot air, enthusiasm
ねっきょう (n,vs) wild enthusiasm, being crazy about
ねっしん (adj-na,n) zeal, enthusiasm
ねっせん (n) fierce fighting, close contest
ねったい (n) tropics
ねったいぎょ (n) tropical fish
ねっちゅう (n,vs) nuts!, enthusiasm, zeal, mania
ねっとう (n,adj-no) boiling water
ねつびょう (n,adj-no) fever, febrile disease
ねつべん (n,adj-no) fervent speech
ねつれつ (adj-na,n) ardent, passionate, vehement

Links: KanjiDic: EDict : Wikimedia
Etymologies: 中文字譜 : 説文解字