Partly True: The longest one-syllable word in the English language is “screeched”.

'Screeched' is among the longest monosyllabic words in the English language which are still in common use.'Screeched' at nine letters long, is among the longest monosyllabic words in the English Language still in common usage. Other nine letter monosyllabic words are 'schlepped', 'scratched', 'scrounged', 'scrunched', 'stretched', 'straights' and 'strengths'. There are some longer monosyllabic words, such as the ten-letter 'scraunched' and 'strengthed', however, those have not been recorded as having been in common usage since the early 17th century. Some lexicographers suggest that other words, longer than nine letters, ought to count as monosyllabic due to the way they are pronounced in certain dialects. Examples include 'squirreled' which can be pronounced as one syllable in some American dialects and 'halfpennyworths' which can be pronounced 'hap'orths in some English dialects.