Someone who is fluent in a particular language can speak the language easily and correctly. You can also say that someone speaks fluent French, Chinese, or some other language.
She studied eight foreign languages but is fluent in only six of them.
她学了8种外语,但能流利运用的只有其中的6种。
He speaks fluent Russian.
他说一口流利的俄语。
If your speech, reading, or writing is fluent, you speak, read, or write easily, smoothly, and clearly with no mistakes.
He had emerged from being a hesitant and unsure candidate into a fluent debater.
他从一个吞吞吐吐、毫不自信的候选人成长为一位口齿伶俐的辩手。