What’s the difference between a 5-year-old native English speaker and a “fluent” English speaker?

With language learning, there’s often an obsession with becoming “fluent” in a language. However, when I see adults bragging about being “fluent” in Spanish/French/or whatever, I’m reminded of how a 5-year-old native speaker is also technically fluent.<br><br>So what’s the difference?<br><br>The 5-year-old is still developing their vocabulary and sometimes pronounces words incorrectly (but in the same way other children do), which doesn’t stop them from being considered fluent. They know all the common idioms and expressions and are able to communicate freely and without issue, and don’t have any sort of detectable accent. <br><br>But adults who have supposedly reached fluency in a new language as an adult still have to deal with a foreign accent, will probably have a smaller vocabulary than a native speaker their age, and may have trouble understanding certain idioms and/or expressions. It feels like the only thing they really have in common with a native speaker is that they can communicate freely, without issue, most of the time.<br><br>So why do people call themselves fluent?