fluency

Concise Oxford English Dictionary © 2008 Oxford University Press:
fluent /ˈfluːənt/

▶adjective

• 1 speaking or writing easily and accurately, especially in a foreign language.

  ■ (of a language) used easily and accurately.

• 2 smoothly graceful and easy.

• 3 able to flow freely; fluid.

– derivatives
fluency noun,
fluently adverb.

– origin C16: from L. fluent-, fluere ‘flow’.