How to say "vapor" in Japanese

• 蒸気じょうきJLPT N2approx.Common
  nounThe default word for vapor as steam, especially water turned to gas by boiling: the steam from a kettle or a steam engine. Choose this for most senses of 'vapor'.
  そのエンジンは蒸気じょうきで動うごく。↗

  The engine is driven by steam.
• 気体きたいJLPT N2approx.Common
  nounReally the word for 'gas': any substance in its gaseous state. It matches 'vapor' only in that scientific sense, as when a substance becomes vapor; it is not the word for visible steam.
  その気体きたいは悪臭あくしゅうを放はなつ。↗

  This gas gives off a bad smell.
• 湯気ゆげJLPT N2approx.Common
  nounSteam you can see rising from hot water or hot food — from a bath, a bowl of soup, or a freshly cooked dish. It is not the word for vapor in scientific senses.
  薬缶やかんから湯気ゆげが立たっている。↗

  The kettle is steaming.

Use 蒸気 for vapor as steam generally, 湯気 for the visible steam rising from hot water or hot food, and 気体 when vapor means a substance in its gaseous state, the sense of 'gas'.

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

• 蒸気じょうきsteam
• 気体きたいgas
• 湯気ゆげsteam
• 息いきsteam (coming off hot food, tea, etc.)