体系
tǐxì · HSK 7
system
🧩 体 body + 系 tie-together = parts tied into one body = a system
体 (tǐ) means body and 系 (xì) means to tie or connect, so 体系 is a set of parts tied together into one organized body — a system or framework of rules.
系 — silk radical 糸 with a stroke on top
Originally a pictograph of a hand holding silk threads, showing connection or lineage. The character depicts threads being tied together, which gave rise to meanings like 'system,' 'lineage,' and 'to connect.' It later became used for organized sequences or relationships.