一瞬
いっしゅん · isshun · JLPT N3 · noun
moment
👁️ 一瞬 = one + blink: an instant is one blink of the eye
瞬 means to blink. Its left side is 目 (eye), so the kanji itself tells you it is about eyes. 一瞬 is literally one blink, the time it takes to blink once. Sound hook: isshun is close to is soon, and an instant is very soon.
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.'