TSUMUGU · TOCFL B1 (est.) · 字
齒
齒 ＝ 齒 ＋ 止
ㄔˇ · chǐ
noun — teeth; a cog, a tooth-like notch (齒輪); age (年齒)
字源 FORM — what the parts do
齒形a mouth full of teeth, drawn in rows
{zh,ch}Izhǐ → chǐ — the initial aspirates from zh to ch
Rows of teeth set in the open mouth — the front teeth. 說文: 象口齒之形. Over them sits 止 zhǐ, marking the sound, aspirated across to chǐ. From the teeth: the cog with its even notches (齒輪) and the years counted off like teeth (年齒).
故事 STORY — a scene to remember it by
一張口（齒）露出整排牙，上面頂著 止（止）——齒。
A mouth (齒) bared to a full row of teeth, capped by 止 — the front teeth.
字源記憶法
意 · Meanings
(本義)牙齒、門齒— teeth, front teeth常用
→齒輪— a gear, a cog
⇒年齒— age, years
(本義) original meaning · → ⇒ each arrow = one more step of extension