高低
gāo dī · HSK 7
height
📏 高低 = high + low; literal 'high-low' covers height, pitch, ups-and-downs
高 means high/tall and 低 means low/short. Stacking the opposites gives a range word: vertical height, musical pitch range, or the highs-and-lows of fortune. Same pattern as 大小 (big-small = size) and 长短 (long-short = length).
高 — pictograph of a tall building/tower
高 is a pictograph of a tall structure, likely a watchtower or multi-story gate, with a roof on top, an upper chamber, and a base below. From this concrete image of height it extended to the general meanings 'tall,' 'high,' and figuratively 'lofty' or 'noble.'
低 — person radical 亻 + 氐 (base)
A semantic-phonetic compound. The left side 亻 (person) gives the meaning, while 氐 supplies the sound and originally depicted something reaching the ground or base. Together they suggest a person bowing low, which extended to the general sense of 'low' in height, position, or degree.