How many letters does the top answer for “(logic and mathematics) a relation such that it holds between an element and itself” have?

The most common answer is reflexiveness (13 letters).

Crossword clue: (logic and mathematics) a relation such that it holds between an element and itself

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

reflexiveness 13 letters wn-def

(logic and mathematics) a relation such that it holds between an element and itself

reflexivity 11 letters wn-def

(logic and mathematics) a relation such that it holds between an element and itself