What does it mean to be a Jew

**EDIT: I don't really care about the definition... I'm trying to understand the reasoning behind it**<br><br>I was raised Orthodox, went to a private school, kept kosher, attended synagogue, did everything a Jewish person was supposed to do. However, when I grew older I realized I was an atheist... I've stopped following most of the traditions<br><br>So, I'm no longer Jewish. I have no right to claim the identity.<br><br>**I just don't see how someone can get a bat mitzvah, yet claim to be an atheist, and still call themselves Jewish.**<br><br>I've read the comments and there's just too many responses to directly respond to<br><br>**I'm asking for an explanation, not your opinion**<br><br>I want to understand the reasoning behind it... why it's totally fine to pretend to be something that you're not, and claim it as your identity.<br><br>I want to understand this perspective because right now I honestly don't get it.<br><br>I want to understand the perspective of Reform and Conservative denominations, and why they claim people likeOMGmaddy as Jewish<br><br>I want to understand why anyone would believe that they "can celebrate all the traditions without believing in God" as if that makes any sort of sense?<br><br>In my eyes it makes even less sense...<br>If you don't believe in God, why in the world would you want to do anything related to religion?<br><br>Please just send me the sources that I should read or whatever