TSUMUGU · TOCFL 2 (est.) · 字
唉
唉 ＝ 口 ＋ 矣
ㄞ · āi
interj — a sigh of regret; an "uh-huh" of response
字源 FORM — what the parts do
矣聲yǐ — gives the sound, slid to āia sentence-ending particle
IF≠yǐ → āi — the donor's reading drifts hard off track
A mouth (口) lets a breath out — the original sense was to answer back (唉,譍也). 矣 yǐ lends the sound, drifted to āi. Today it leans into the long exhale of regret: 唉聲嘆氣.
故事 STORY — a scene to remember it by
一口氣從嘴（口）裡放出來，肩膀也跟著垮下——唉。
A breath let go through the mouth (口), the shoulders dropping with it — a sigh.
字源記憶法
意 · Meanings
(本義)應答— to answer back, respond
→唉、唉聲嘆氣— a sigh of regret常用
(本義) original meaning · → ⇒ each arrow = one more step of extension