smoothnessnoun [ U ]
us/ˈsmuð·nəs/smoothness noun [ U ] (BEING WITHOUT INTERRUPTION)
the fact of happening or being done without any sudden changes, interruption, or difficulty:
The car delivers power with the smoothness of a jet engine.
smoothness noun [ U ] (BEING REGULAR)
the quality of being perfectly regular, with no holes or lumps or areas that rise or fall suddenly:
I love the smoothness of silk