fluency [ˈfluːənsɪ]
noun
1 (in foreign language) fluidez (f); soltura (f)
she speaks French with great fluency habla francés con mucha fluidez or soltura; domina bien el francés; you need fluency in at least one foreign language necesita dominar al menos una lengua; I was impressed by his fluency in English me impresionó su dominio del inglés