How many letters does the top answer for “by experiment; by experience or trial. j. s. mill.” have?

The most common answer is experimentally (14 letters).

Crossword clue: by experiment; by experience or trial. j. s. mill.

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

experimentally 14 letters web-def

in an experimental fashion

to make experiments (upon); to experiment. j. s. mill. 50% similar → experimentalize