Readability
Readability is how easily a text can be read and understood because of its vocabulary and sentence construction, regardless of typography
What it means, how it is used and where it comes up, with its related concepts.
What it is and how it works
It is distinct from legibility, which depends on typographic design: size, contrast, line spacing or letterforms. A text can be perfectly legible and still hard to understand.
It is estimated with formulas combining word length, measured in syllables, and sentence length, such as the Flesch Reading Ease score. Because Spanish uses longer words than English, there are specific adaptations, such as the Fernández Huerta formula, the Szigriszt-Pazos perspicuity index and the INFLESZ scale. These formulas offer guidance but do not assess structure, the order of ideas or whether the text meets the reader’s needs; plain language and easy-to-read approaches address those aspects.