Several parts combine into one character.

渡 is a phonetic-semantic compound: 氵 (water) plus 度 (measure / degree / regulation). The composite suggests "to cross water at a measured, regulated point" — a controlled river crossing at a designated ford or ferry. From this concrete riverside image the meaning extended into "to transfer, to hand over, to pass through a transitional period."

Korean reading "do." Largely formal Sino-Korean: 讓渡 (yangdo, transfer / cession of property), 過渡 (gwado, transition), 渡江 (dogang, crossing a river), 渡海 (dohae, crossing the sea). 渡 alone is rare in modern Korean conversation — it lives in legal, historical, and literary contexts.

Mandarin dù, 4th tone. 渡过 (dùguò, to cross over / get through difficulty), 过渡 (guòdù, transition — political or developmental), 让渡 (ràngdù, to transfer rights), 渡轮 (dùlún, ferry boat). The metaphorical sense "get through hard times" — 渡过难关 (dùguò nánguān, to get through a tough patch) — is widely used in Chinese commentary and counsel.

Japanese is where 渡 becomes most active. On-reading ト (to) — 渡航 (tokō, overseas voyage / sea travel), 譲渡 (jōto, transfer / cession). The kun-readings make a critical Japanese grammatical distinction: わたる (wataru, intransitive — "to cross over by oneself") vs わたす (watasu, transitive — "to hand over to someone"). 橋を渡る (hashi o wataru, to cross the bridge — subject moves) vs 鍵を渡す (kagi o watasu, to hand over the key — object moves to someone). This intransitive/transitive pair is one of the cleanest examples of the わたる/わたす, あがる/あげる pattern that defines Japanese verb morphology.

Memory aid: water (氵) + measure (度) — crossing water at a measured point.