How many letters does the top answer for “capability of being demonstrated or logically proved” have?

The most common answer is demonstrability (15 letters).

Crossword clue: capability of being demonstrated or logically proved

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

demonstrability 15 letters wn-def

capability of being demonstrated or logically proved

provability 11 letters wn-def

capability of being demonstrated or logically proved

capable of being demonstrated or proved 50% similar → provable