How many letters does the top answer for “using or knowing two languages” have?

The most common answer is bilingual (9 letters).

Crossword clue: using or knowing two languages

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

bilingual 9 letters wn-def

a person who speaks two languages fluently

using or knowing three languages 60% similar → trilingual

using or knowing more than one language 50% similar → multilingual

using or knowing only one language 50% similar → monolingual