How to say "fever" in Japanese

• フィーバーCommon
  noun, suru verb, intransitive verbCovers only the figurative sense: a fever of excitement or enthusiasm. It does not mean a raised body temperature, so it is not the word for being ill with a fever.
• 熱病ねつびょうCommon
  no-adjectiveRefers to fever as an illness — a febrile disease — rather than to the symptom of having a temperature; for that, 熱 is the everyday word.
• 熱ねつJLPT N4approx.Common
  nounCovers the literal sense of fever — a raised body temperature — as well as temperature itself; when someone is sick with a fever, this is the word.
  １０２゜Ｆの熱ねつがあります。↗

  I have a fever of 102 degrees.

For a raised body temperature use 熱; 熱病 treats fever as a febrile disease; 「フィーバー」 is the loanword for fever as a state of excitement, not for illness.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• フィーバーfever (state of excitement)
• 熱病ねつびょうfever
• 熱発ねっぱつfever
• 熱ねつfever
• 熱気ねっきfever
• 発熱はつねつ(attack of) fever