From Teflpedia

Readability (/ri:dəbɪlɪti/) is the ease with which a reader (e.g. a student) can understand a written text. It is a type of comprehensibility.

Otherwise, there are various readability statistics that attempt to quantify the readability. A high readability score means something is difficult to read.

Students being able to understand[edit | edit source]

Considering the receptive skill of student reading, this is broadly dependent on two factors; (1) how good the student is at reading, and (2) how difficult the text is.

For graded readers, headword count is often used as a proxy for readability.

Being able to understand students[edit | edit source]

The flipside of this is that students produce written texts in learner English, which will be read either by the teacher and/or other students and/or others. Students make errors which may reduce readability, such as spelling mistakes, grammatical errors, and poor handwriting.