constancy
noun [ U ] formal uk/ˈkɒn.stən.si/ us/ˈkɑːn.stən.si/
(STAYING SAME)
恒久不变；稳定
the quality of staying the same, not getting less or more
(LOYALTY)
忠诚
loyalty
Never doubt the constancy of my love for you. 永远不必怀疑，我对你的爱忠贞不渝。