Thread, yarn, or string — a thin cord used for sewing or knitting; can also be used figuratively. Also used as a suffix in compounds.
セーターを編むために毛糸を買った。
I bought yarn to knit a sweater.
糸が途中で切れてしまった。
The thread snapped midway.
その話には細い糸でつながった因果関係がある。
That story has a causal relationship connected by thin threads (figurative).