How easily a thing can be taken in by whoever meets it. Readability is a property of the writing, never of the reader.
Built on read, from Old English rædan (to interpret, to read) + the Latin-derived suffix -ability; readability names a property of the text rather than of whoever meets it.
How easily a thing can be taken in by whoever meets it. The root places the property correctly: readability belongs to the writing, never to the reader who is struggling with it.