Both I and J were used interchangeably by scribes to express the sound of both the vowel and the consonant. It wasn’t until 1524 when Gian Giorgio Trissino, an Italian Renaissance grammarian known as the father of the letter J, made a clear distinction between the two sounds.
n., pl. Js J's, js j's. 1. the tenth letter of the English alphabet, a consonant. 2. any spoken sound represented by this letter. 4. a written or printed representation of the letter J or j. Symbol. the tenth in order or in a series. Math Symbol.
( pharmacy, obsolete) one . The tenth letter of the English alphabet, called jay and written in the Latin script. In Spanish language loanwords and names, "j" is pronounced as an "h", for example in fajita and Julio. In Scotland, this letter is sometimes spelled jy, to reflect the local pronunciation.