spoken or written with ease

fluent French.

able to speak or write smoothly, easily, or readily

a fluent speaker; fluent in six languages.

easy; graceful

fluent motion; fluent curves.

flowing, as a stream.

capable of flowing; fluid, as liquids or gases.

easily changed or adapted; pliant.

noun

volubility , eloquence , facility , fluidity , facundity , grandiloquence , liquidity , loquaciousness , loquacity , mellifluence , verbosity