Where the shape comes from
A small loop of silk thread, the topmost coil of a skein — a reduced sketch of the same fibre pictured whole in 糸. Paired with 力, strength, it gives 幼, young, someone whose strength is still as slight as a single thread; doubled, the same loops crowd together in 兹, a thicket of growth, and in 幾, a guard straining to watch for the faintest, thread-thin sign of danger.
汉字 filed under 幺
No published character on HSK Guide is filed under this radical yet. 汉字库.