Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
4to is a noun meaning "the size of a book whose pages are made by folding a sheet of paper twice to form four leaves". It carries one recorded sense.
Definitions, synonyms and semantic relations for 4to come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.