ibility

ibility is a noun-forming suffix in English used to express the quality, condition, or state of being able to do something. It is part of the larger -ility family and is typically appended to adjectives ending in -ible to form abstract nouns such as credibility, feasibility, legibility, and audibility. The suffix traces to Latin -ibilitas and became part of English through Old and Middle English development.

In practice, -ibility is most productive with adjectives that end in -ible. Examples include credible → credibility, feasible → feasibility, legible → legibility, and audible → audibility. The resulting nouns denote the extent or possibility of the property described by the adjective. Some words contain the sequence -ibility as part of a longer word where the end of the word also carries -ty or -ity, as in visibility or invisibility, though the functional suffix remains -ibility within the word’s morphology.

Usage and nuance: -ibility often conveys a more objective or formal assessment of a quality or possibility, especially in technical, scientific, or evaluative writing. There is overlap with the related suffix -ability, which more commonly forms nouns from -able adjectives. Although the distinction is not absolute, -ibility tends to follow -ible forms, while -ability follows -able forms, with many exceptions in everyday vocabulary.

See also: -ability, -ity, -ible, -able, English morphology.