深い
ふかい · fukai · JLPT N4 · i-adj
deep
🌊 fukai sounds like far-kay: the far-down K, deep below the surface
深 pairs the water radical 氵 with a part meaning to probe, so it is literally water you have to probe to find the bottom. The same word covers deep feelings and profound ideas, just as deep does in English.
深 — water radical 氵 + 罙 (phonetic, depth)
深 combines the water radical 氵 with 罙, which depicts a hand reaching into a cave or hollow. Originally it described deep water, then broadened to mean 'deep' in any sense — distance, color, or feeling. The 氵 gives the meaning, while 罙 hints at both sound and the idea of reaching far in.