Ok, Lets be less vague with the wording I used, since these proficiency levels aren’t easy to define.
Fluency is the ability to read a text accurately, quickly, and with expression. It provides a bridge between word recognition and comprehension. When fluent readers read silently, they recognize words automatically. They group words quickly to help them gain meaning from what they read. Let’s use the same definition when talking about speaking: smoothness or flow with which sounds, syllables, words and phrases are joined together when speaking quickly.
Native speaker has the same definition as above but seen from the boots of a local: it dominates his mind and is therefore the language he does his thinking in.
TBH, I doubt any of us will ever earn the native badge. Some of you are making your point about feeling the fluency of your mother tongue, which is out of discussion; it should be in reference to non-native languages. I would even say Japanese is in a completely different league; It’s far easier for Frenchies, Spaniards, etc. to learn English, and vice versa. *
So, let’s say proficient instead of fluent, and fluent instead of native. Fair enough?
* Let’s not include Arabic, Chinese, Pak Tai, etc. for the sake of my argument