What is the longest one syllable word in the english language?

There are a number of nine-letter words of a single syllable. Unsurprisingly, most of these long words contain one or more digraphs (e.g., rr or ai) and the occasional trigraph (e.g., tch). That is, multiple letters are used to represent a single sound. Additionally, neither the -ed preterite past tense ending for verbs, nor the -s plural ending for nouns increases the syllable count for words, so it is unsurprising that the longest words would use these endings. {However, the final -ed ending WILL INCREASE the syllable count if the verb base ends in a /t/ or /d/ sound: divide becomes divided (two syllables become three) and create (two syllables become three) or in a one-syllable word such as rent (rented the one syllable becomes two).