---
title: "Comprehensible input — what it means · NoaLingua"
description: "Comprehensible input is language you mostly understand but not entirely — the level at which exposure teaches you something. How to find it."
url: "https://noalingua.com/glossary/comprehensible-input/"
language: "en"
modified: "2026-08-21"
license: "CC BY 4.0 — https://creativecommons.org/licenses/by/4.0/"
---
Glossary

# Comprehensible input — the NoaLingua glossary

Comprehensible input is language you can mostly understand but not entirely — the level at which exposure teaches you something new.

The term comes from Stephen Krashen's input hypothesis, which argues that acquisition happens when you understand messages slightly beyond your current level rather than when you study rules about them.

The practical problem is finding it. Material at your exact level is rare, and the honest test is not whether a video feels hard but what proportion of its words you actually know. Below roughly 90 per cent you are decoding rather than acquiring; above 98 per cent you are enjoying yourself and learning very little.

In NoaLingua The transcript panel estimates a video's difficulty by comparing every word spoken against your own deck, and the PDF reader shows what percentage of a document is words you already know. Both are measures of a specific text against you, rather than a general reading level.

## Where this shows up in NoaLingua

- [How to choose comprehensible input](https://noalingua.com/blog/comprehensible-input-choosing-material/)
- [Vocabulary size and lexical coverage](https://noalingua.com/blog/how-many-words-do-you-need/)

## Sources

Research and official documentation used for this definition.

- Research [Unknown vocabulary density and reading comprehension](https://nflrc.hawaii.edu/rfl/item/43) Hu Hsueh-chao & Paul Nation, Reading in a Foreign Language, 2000 The empirical basis for discussing lexical coverage. Its thresholds come from one reading experiment and are guidance, not a universal pass mark.
- Research [How large a vocabulary is needed for reading and listening?](https://openaccess.wgtn.ac.nz/articles/journal_contribution/How_large_a_vocabulary_is_needed_for_reading_and_listening_/12552221) Paul Nation, Canadian Modern Language Review, 2006 Vocabulary-size estimates for high lexical coverage of unsimplified written and spoken English.

## Related terms

[i+1 i+1 describes material containing exactly one unknown element beyond your current level — the theoretical ideal for acquisition.](https://noalingua.com/glossary/i-plus-1/)[Immersion Immersion is spending large amounts of time with material made for native speakers, rather than with material made for learners.](https://noalingua.com/glossary/immersion/)[Frequency list A frequency list ranks the words of a language by how often they occur in a large body of real text.](https://noalingua.com/glossary/frequency-list/)

## Try NoaLingua on the next video you were going to watch anyway.

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