沿

A phono-semantic compound:

水 (수) — semantic component, indicating water / flow

㕣 (연) — phonetic component, supplying the sound (연 / yán)

The original sense is “to move following the course of water”, i.e., along a river or stream.

From this concrete spatial image developed the broader meaning “to follow along” any continuous line or boundary.

Semantic development:

- following water flow — along a river

- linear following — roads, coasts, borders

- procedural following — following rules or customs (figurative)

沿 is common in spatial descriptions, routes, and procedural following.

Common compounds and constructions:

연안 (沿岸) — along the coast

연해 (沿海) — coastal; along the sea

연로 (沿路) — along the road

연선 (沿線) — along a railway/line

연습 (沿襲) — to follow tradition; inherit by custom

Modern Chinese patterns:

沿着河走 — walk along the river

沿路查看 — inspect along the way

Unlike 隨 (to follow freely), 沿 emphasizes adherence to a fixed path or boundary.

Related characters (following & path):

隨 — to follow (freely)

循 — to follow; to comply

依 — to rely on; follow

順 — to obey; go along

道 — road; path

Among these, 沿 uniquely denotes following a physical or conceptual boundary.