主轴

axis / principal axis (in mechanics, optics, botany etc) / main axle (of engine)

owner / master / host / individual or party concerned / God / Lord / main / to indicate or signify / trump card (in card games)

axis / axle / spool (for thread) / roller (for scrolls) / classifier for calligraphy rolls etc

see 壓軸戲|压轴戏[ya1 zhou4 xi4] / Taiwan pr. [zhou2]

main bearing