What is the longest one-syllable English word?

The one that's most commonly cited is screeched (nine letters). But there are also scratched, scrounged, scrunched, stretched, and the plural nouns straights and strengths (all with nine letters).

The 20-volume historical Oxford English Dictionary also has scraughed, scrinched, scritched, scrooched, sprainged, spreathed, throughed, and thrutched. It  includes, too, a single instance of the ten-letter word scraunched, from the 1620 English translation of Don Quixote, a novel by the Spanish writer Miguel de Cervantes.