What is it?
The ability to speak or write a foreign language easily and accurately and to comprehend most communication.
Why is it important?
Fluency enables the user of a language to focus on making connections among ideas. By making connections, the reader can focus his/her attention on comprehension. For most languages, fluency means having a minimum of 15,000 to 20,000 words in your vocabulary and being able to use them correctly in context[Liedel 2014].