息|いきiki[1]atamadaka (head-high)

1. nounbreath; breathing
   おぼれかけた人ひとは息いきを吹き返ふきかえした。↗

   The man who nearly drowned began to breathe.
2. nounconcord; harmony; rapport
   彼かれらは息いきがぴたりと合あっている。↗

   They are a perfect match for each other.
3. nounsteam (coming off hot food, tea, etc.); (water) vapor; vapour

• Synonym呼吸こきゅうNeutralRefers to breathing as an act or bodily function, in both everyday and medical use, e.g. 「呼吸が苦しい」. 「息」 turns up in many idioms, like 「息が合う」.
• Synonym気息きそくWrittenA written word for breath or breathing, seen mostly in literature and phonetics. In daily conversation, say 「息」 or 「呼吸」 instead.
• Related息吹いぶきWrittenA written word: it can mean breath, but more often figuratively the vitality of something new, as in 「春の息吹」. 「息」 is plain breath, and can also mean rapport.

For everyday talk about breath or catching your breath, use 「息」. For breathing as an act or bodily function, 「呼吸」 is the usual choice. 「息吹」 is a literary word for the breath or vitality of something new; 「気息」 is formal written prose.

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

1. （いき）呼吸こきゅう。呼気こき。