quality - an essential and distinguishing attribute of something or someone; "the quality of mercy is not strained"--Shakespeare

legibility, readability - writing (print or handwriting) that can be easily read

intelligibility - the quality of language that is comprehensible

clarity, clearness, limpidity, lucidity, pellucidity - free from obscurity and easy to understand; the comprehensibility of clear expression

coherence, coherency - logical and orderly and consistent relation of parts