唯一
ゆいいつ · yuiitsu · JLPT N3 · na-adj
only
☝️ 唯一 = only + one: the one and only
唯 means only or solely, and 一 is one, so 唯一 is literally only-one. Sound hook: yuiitsu sounds like you-eat-su: you eat the sole, unique piece.
唯 — mouth 口 + short-tailed bird 隹
A semantic-phonetic compound: 口 (mouth) gives the meaning related to speech or response, while 隹 (short-tailed bird) supplies the sound. Originally meant 'to answer' or an affirmative reply, later extended to 'only' or 'alone'.
一 — single horizontal stroke
一 is one of the simplest pictographs in Chinese, depicting a single horizontal line to represent the number one. It has retained essentially the same form since oracle bone script over 3,000 years ago. By extension it also means 'first,' 'whole,' or 'same.'