He was son of John Kersey the elder, with whom he has often been confused, and revised the work of his father in the fourteenth edition of the Arithmetic of Edmund Wingate (1720).
He, more probably than his father, contributed the Discourse to an unlearned Prince' to the Translation of Plutarch's Morals, which appeared 1684-5 (republished 1870).
About this work, Starnes & Noyes said "Kersey's vocabulary, estimated at 35,000 words, far surpasses that of any preceding dictionary, with the single exception of the folio Kersey-Phillips, which, amazingly enough considering its difference in physical size, it almost equals."
The first decade of the eighteenth century had produced five new dictionaries, and its lexicography had been dominated by the activities of John Kersey.
Kersey was...a notable pioneer, rejected outmoded material and methods, working toward modern concepts, and in general playing his role of lexicographer with responsibility and intelligence.