TSUMUGU · TOCFL 1 · 字
空
ㄎㄨㄥ · kōng/kòng
adj — empty; noun — sky, air; (kòng) free time, a free spot
字源 FORM — what the parts do
{g,k,h}Igōng → kōng — g stepped to k inside {g,k,h}; the same 工 reads h in 紅
A cave (穴) with 工 for sound, g stepped to k — a hollow. Nothing inside: empty; the widest hollow overhead: 天空、空氣. Read kòng, the hollow is yours to use: 有空、空位.
故事 STORY — a scene to remember it by
山壁上一個洞（穴），探頭進去喊一聲——只有回聲。
A cave (穴) in the cliff; a shout into it — only the echo comes back.
字源記憶法
意 · Meanings
kōng
(本義)中空— hollow — the cave's inside
→空、空的— empty常用
→天空、空氣— the sky, the air常用
kòng
(引申)有空、空位— free — an unfilled hour, an unfilled seat常用
(本義) original meaning · → ⇒ each arrow = one more step of extension