Most language courses start with a textbook, a vocabulary list, and a grammar table. They’re built around what’s easy to teach, not around how the brain actually learns. After more than forty years of working at the intersection of psychology, linguistics, and learning design — and after learning Mandarin Chinese myself in six months — I’ve identified five principles that underlie rapid language acquisition. These aren’t tips or tricks. They’re the foundations. Get these right, and everything else accelerates. Get them wrong, and no amount of study hours will save you. I laid these out in my TEDx talk, “How to Learn Any Language in 6 Months.” Here, I’ll go deeper into each one, and explain why they matter whether you’re learning Mandarin, Japanese, Spanish,…