呼吸
こきゅう · kokyuu · JLPT N3 · noun
breath
🫁 呼吸 = breathe out (呼) + breathe in (吸): a full breath
呼 (ko) means to call out or exhale; 吸 (kyuu) means to suck in or inhale. Put out-breath and in-breath together and you get respiration. The 口 mouth radical on both kanji marks them as mouth actions.
吸 — mouth radical 口 + reach 及 (phonetic)
吸 is a phono-semantic compound. The mouth radical 口 signals the meaning—an action done with the mouth—while 及 (jí) hints at the original sound. It depicts drawing air or liquid in through the mouth, giving the modern senses 'inhale, suck, absorb'.