hectometre, (kokuji)
粨 is a Japanese-made kanji (kokuji) for the metric unit hectometre (100 metres). Its meaning is a specific measurement, not a general concept.
粨 is a modern kokuji created in Japan by combining 米 (metre) and 百 (hundred) to represent hectometre. It has no ancient historical origin.
The left side 米 stands for metre, and the right side 百 means one hundred. Together they form a hectometre: one hundred metres.
For ヘクトメートル, the reading is the direct loanword 'hectometre' in katakana. Think of the kanji as a label: 粨 = ヘクトメートル, a hundred-metre unit.
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