Lub rotation axis yog cov kab geometric uas qhov kev ua rotationally symmetric yog ua. Lub axis ntawm kev sib hloov yog cov kab geometric raws li qhov kev sib hloov symmetrically tshwm sim. Thaum qhov kev sib hloov ua haujlwm ntawm cov duab (los yog cov qauv), qhov ntsug nrug ntawm ib qho taw tes hauv daim duab thiab cov axis tig (kab) yuav tsum nyob twj ywm tas li.
