TSUMUGU · TOCFL 3 (est.) · 字
域
ㄩˋ · yù
noun — region, territory, domain, field
字源 FORM — what the parts do
FThuò → yù — the reading shifts
或 was the original word: a halberd (戈) standing guard over a bordered area — a territory you defend. When 或 drifted off to mean "perhaps," earth (土) was added to hold the land-sense: 域, a marked-off region. The same 或 also got walled (囗) into 國, the state. From the guarded ground come 區域、範圍, then the figurative 領域 (a field of study).
故事 STORY — a scene to remember it by
一桿戈（戈）守著一塊地，外加土（土）劃下界——界裡是域。
A halberd (戈) guards a patch of ground, earth (土) drawing the line — inside the line is 域.
字源記憶法
意 · Meanings
(本義)區域、疆域— territory, region常用
→範圍— bounded area, range
⇒領域— field, domain (of study or work)常用
(本義) original meaning · → ⇒ each arrow = one more step of extension