Comprehensible input (CI) means language that students receive which they can understand, or comprehend. In CI approaches, students acquire the meaning of the second language in a natural way, often through gestures, movements, and visuals. This approach was championed by researcher Stephen Krashen, and is closest to how humans learn their first language. It is also considered more enjoyable than other forms of language learning, such as memorizing vocabulary or sentence chunks and putting them together.