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Glossary

LIX Readability Index

What is LIX Readability Index?

LIX (läsbarhetsindex) is a readability measure developed in Sweden by Carl-Hugo Björnsson. It adds the average sentence length in words to the percentage of long words with more than six letters. Example: 15 words per sentence and 30% long words give a LIX of 45. As it does not require syllable counting, it can be applied to many languages, including German; low scores indicate easy texts and scores from around 60 very difficult ones.

How KI.ordo helps

KI.ordo's “Check and simplify readability” template assesses factors such as sentence length and technical terms, which also feed into LIX, and suggests an easier-to-read version.

Learn more →: LIX Readability Index

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  • Readability
  • Metric
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Related terms

Readability

Readability describes how easily a text can be read and understood. It depends on sentence length, word length, technical terms, sentence structure and layout, and can be approximated with formulas such as the Flesch index or LIX. Good readability matters for customer communication, instructions, websites and accessible content. Formulas only offer guidance, however; whether a text is clear ultimately depends on its audience.

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Flesch reading ease

The Flesch reading ease score estimates how easy a text is to understand, based on average sentence length and the number of syllables per word. Rudolf Flesch developed it for English in 1948, and adapted formulas exist for other languages. The scale runs roughly from 0 to 100 – the higher the score, the easier the text. It measures form only, not whether the content and terminology suit the intended audience.

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Grade Level

In readability research, grade level is a measure of the school year from which a text is generally understood. A well-known example is the Flesch–Kincaid Grade Level, which calculates a US school grade from sentence length and syllables per word; a score of 8 roughly corresponds to eighth grade. Such scores transfer only partly to other languages, so adapted formulas such as Amstad's version of Flesch or LIX are often used for German.

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Reading Level

Reading level indicates the level of reading ability a text requires or a person has reached. Depending on the system, it is expressed as a school grade, a value on a scale such as Lexile, or a level in curricula and language frameworks, such as A2 or B1 in the Common European Framework of Reference. In practice, it helps tailor texts to the intended audience, for example customer information in plain language.

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