枢纽
shū niǔ · HSK 7
hub
🔗 枢 (door pivot/hinge) + 纽 (knot, tie, button) = the pivotal knot where everything ties together
枢 originally meant the pivot a door swings on; 纽 is a knot or button that fastens things. Together they name the central tie-point a whole network turns on: a hub, hinge, or fulcrum.