The quality or state of being allowable; how much something is permitted or acceptable.
From 'allowable' plus the suffix '-ness,' which forms abstract nouns describing qualities or states. The suffix '-ness' comes from Old English and has been used for over a thousand years to nominalize adjectives.
While 'allowability' sounds more modern, 'allowableness' is the historically correct form that appeared in 18th and 19th-century legal texts, showing how English once preferred '-ness' for almost all adjective-to-noun conversions before we started mixing in Latin-style endings.
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