指数
zhǐshù · HSK 6
index
📊 zhǐ (finger/point) + shù (number) = the number that points to scale
A finger pointing at numbers on a scale — that is an index. In math, the exponent is the small number that indicates how many times to multiply. Both senses share the idea of a number that indicates something.
指 — hand radical 扌 + 旨 (zhǐ, phonetic)
指 is a semantic-phonetic compound. The hand radical 扌 gives the meaning — something done with the hand, namely pointing with a finger. 旨 supplies the sound 'zhǐ'. From 'finger' it naturally extended to the verb 'to point' and figurative senses like 'to indicate' or 'to refer to'.
数 — 婁 (lóu, phonetic) + 攵 (action radical)
数 is a phono-semantic compound. The right side 攵 (a hand holding a stick) suggests an action, originally tallying or counting by striking marks. The left side 婁 supplies the sound. Over time the meaning broadened from 'to count' to 'number' and 'several'.