not only (... but also ...)
不 (bù) · 4 strokes
Pictograph of sepals of a flower. The modern meaning "no" is a phonetic loan.
但 (dàn) · 7 strokes
Phonosemantic compound. 亻 represents the meaning and 旦 represents the sound. Based on the original meaning "bare-chested". The current meaning is a phonetic loan.