Comprehensible Input is a concept introduced by linguist Stephen Krashen. It describes language that someone can understand even if they don’t know every word or grammar rule.

We don’t acquire language by memorizing rules or drilling grammar. We learn it by understanding messages. When you read or hear something and the meaning is mostly clear from context, that’s comprehensible input.

You don’t need to understand every word. A few unknown phrases are fine as long as the overall message makes sense. That bit of challenge helps you stay focused and absorb more naturally.

The more input you get, the more your brain gets used to the language. You don’t need to study in a traditional way. Just keep reading and listening to things you mostly understand, and the language will start to stick.

Benefits of CI

• Learning without memorizing word lists
• Better listening and reading over time
• Improved long-term memory for patterns
• More motivation through interesting content

How to get started

• Watch YouTube channels with Japanese subtitles or simple native speech
• Listen to podcasts that speak slowly and clearly
• Read manga or easy books that you actually enjoy
• Revisit content you’ve liked before

All of this is input. If you mostly understand it and it holds your attention, you’re learning. Keep listening and reading. Your brain will take care of the rest.

Watch Krashen explain it himself

In this lecture from the 1980s, linguist Stephen Krashen answers a key question in language learning: How do we acquire language?

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For more details, Krashen’s book “Principles and Practice in Second Language Acquisition” is available online for free.