海峡
かいきょう · kaikyou · JLPT N1 · noun
channel
🌊 海 (sea) + 峡 (narrow gorge) = a sea squeezed through a narrow gap = strait
The kanji 海 means sea and 峡 means gorge or narrow valley. A strait is a narrow stretch of sea between two landmasses, so the compound describes it directly.
海 — water radical 氵 + 每 (phonetic)
海 is a phono-semantic compound. The 氵 (water) radical signals the meaning—a vast body of water—while 每 supplies the sound. Originally referring to the sea or ocean, it later extended figuratively to mean 'vast' or 'a great quantity,' as in 人海 (a sea of people).