What makes *someone* a native speaker?

LIZ LI wrote:

If you're a native Italian, you'll understand why it's "illegal" put pineapples on pizza. (vs Hawaiin)
If you're a native Chinese, you'll understand why it's "forbidden" to make sweet Xiaolongbao (steamed minibuns). (vs Japanese)
And the list may keep going on

Denis Fesik wrote:

Being a native speaker of whichever language, am I supposed to follow TV shows? And what if I don't? Am I supposed to know teen slang? What about the history of teen slang? And how far back? How many memes am I supposed to keep in mind? Over here, it's okay not to stay up to date with the latest language trends, you might as well speak a century old language and that won't sound too weird. The wording of the topic starter's question makes it too easy to answer, but if we're talking about someone achieving native-level knowledge of a language, then it is almost impossible to answer. They say, three year old kids can make it, but what if it's three years and one month? So, my niece won't achieve native level in English because she started learning it at six, but one of her friends might, because I think she lived in London at a much younger age. But what if there are exceptions? Is there a test for whether your brain can no longer absorb languages the way a kid's brain does? Anyway, my English classes started when I was about fifteen (my first foreign language was German), but I'm not claiming native level, am I?

[Edited at 2021-09-16 07:33 GMT]

LIZ LI wrote:
what's the difference between native and near-native? How "near" is that? And what on earth is in between them?

Korana Lasić wrote:

Someone who's internalised a language at a very young age, before they started learning it in any structured way. I also think that if someone thinks, dreams, and makes love in a certain language, that's a good indication of them being native speakers of it. Some people do this in more than one language and that makes them bilingual.