noun
Refers to the shaft on which a wheel rotates, used in vehicles and machinery.
車軸に油を差す。
I oil the axle.
車軸が折れて、車輪が外れた。
The axle broke and the wheel came off.
車輪 means 'wheel', while 車軸 is the axle that the wheel rotates on.
Compound of 車 (sha, 'vehicle') and 軸 (jiku, 'axis, shaft').