便箋
びんせん · binsen · JLPT N2 · noun
writing paper
📝 便 = letter/mail (as in 郵便) + 箋 = note paper: paper for writing letters
便 here means post or message, as in 郵便 (mail). 箋 is a slip of writing paper. Together they name the everyday paper you write letters on.
便 — person 亻 + change 更
A semantic compound: 亻(person) beside 更 (to change/replace). The original sense was a person making things easier or more convenient by adjusting them. From 'convenient' it extended to 'then/thereupon' (biàn) and to bodily 'discharge' (as in 大便).