How many letters does the top answer for “doctor (abbreviation)” have?

The most common answer is dr (2 letters).

Crossword clue: doctor (abbreviation)

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

dr 2 letters orig-abbr

doctor of medicine (abbreviation) 67% similar → md

doctor of philosophy (abbreviation) 67% similar → phd