Legibility

[Lej-uh-bil-i-tee]

noun

Also leg·i·ble·ness

The state or quality of being legible.

Legibility is defined as the “capability of being discovered or understood” or the "capability of being read or deciphered".

Legibility is the clarity of visually-presented text, affected for instance by the size of the text, the contrast between similar letters, the quality of printing or display (whether the text is damaged or blurred), the line-spacing and word-spacing, and the shape and style of individual letters.

Other influencing factors

Environmental conditions or interferences, such as lighting or vibrations (e.g. from walking), which affect the human visual system
The viewing distance (i.e. the angular size of the symbols)
The reproduction quality (e.g. sufficient brightness contrast between symbols and their background), which may be limited by the technology of the presentation medium
Abilities and fitness of the readers

It is also called visibility in typography, namely the quality of type that affects the perceptibility of a word, line, or paragraph of printed matter.

In everyday language, legibility is commonly used as a synonym for readability. In graphic design, however, legibility is often distinguished from readability.

Readability is the degree to which the meaning of text is accessible, based on the complexity of sentences and the difficulty of the vocabulary that is used.