深信
shēn xìn · HSK 7
to believe firmly
🤝 深 deep + 信 trust = trust deeply = to believe firmly
深 means deep and 信 means trust or believe. Stack them: a belief held at depth, not on the surface. The same 信 appears in 相信 (to believe) and 信任 (to trust).
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.
信 — person 亻 + speech 言
信 combines 亻(person) with 言(speech), depicting a person standing by their words. The original sense is 'truthfulness' or 'sincerity'—what a person says can be trusted. From this it extended to 'believe,' 'trust,' and later 'message' or 'letter,' since a letter carries one's word.