课本
kèběn · HSK 1
textbook
📖 课本 = lesson + root/book = textbook (the root book for each lesson)
课 means lesson or class; 本 originally meant the root of a tree and came to mean a bound book or volume. Together they name the core book tied to a course of lessons.
课 — speech radical 讠(言) + fruit/result 果
课 is a semantic-phonetic compound. The left side 讠(言 'speech') gives the meaning, since the original sense involved oral examination or assessment. The right side 果 ('fruit, result') supplies the sound 'guǒ', which shifted to 'kè'. The meaning later broadened from 'test' to 'lesson' or 'class'.
本 — tree 木 + mark at base
本 is a pictograph of a tree (木) with a stroke at its base, marking the roots. From this 'root' meaning it extended to 'origin,' 'source,' and 'foundation.' In modern usage it also serves as a measure word for bound objects like books.