While sitting in the tenth place in the English alphabet, the letter J, which split off from the letter I, was actually the last addition to the writing system.
“J” is a bit of a late bloomer; after all, it was the last letter added to the alphabet. It is no coincidence that /i/ and /j/ stand side by side – they actually started out as the same character. The letter /j/ began as a swash, a typographical embellishment for the already existing /i/. With the introduction of lowercase letters to the Roman numeric system, /j/ was commonly used to denote the conclusion of a series of one’s – as in “xiij” for the number 13.