零

Top 雨 is the indexing rain radical - drops falling from a cloud bar, with four inner dots as the rain itself. Anchors 零 in the weather family. The original meaning was 'scattered drizzle', which generalised to 'odd bits' (零钱 small change, 零碎 fragments) and finally to the abstract 'zero'. Same radical: 雷, 雪, 露, 霜.

Bottom 令 supplies the sound - lìng drifting to líng (only tone shifts). Same phonetic family: 龄 age, 铃 bell, 玲 tinkle, 邻 neighbour. Pure phonetic; the 'command' meaning of 令 contributes nothing. The whole 令-cluster gives the líng / lìng / lín rhyme group.