fluency /ˈfluːwənsi/ noun Learner's definition of FLUENCY
[noncount]
1
: the ability to speak easily and smoothly(说话)流利 especially : the ability to speak a foreign language easily and effectively(尤指外语)流利,流畅 2
: the ability to do something in a way that seems very easy(做事)流畅,娴熟