THE LETTER J OF THE ALPHABET. This letter was not differentiated from I until com paratively modern times. It was the custom in mediaeval mss. to lengthen the letter I when it was in a prominent position, notably when it was ini tial. As initial I usually had consonantal force, the lengthened form came definitely to be regarded as representing the consonant and the shortened form the vowel in whatever position they occurred. The process of differentiation began about the i4th cent. but was not complete till the 17th. For certain purposes, an alphabetical series for example, the letters I and J are not even yet regarded as distinct, the enumeration passing generally from I to K.
The original consonantal sound represented by the letter was the semi-vowel or spirant i (the sound of y in the word yacht). This passed into dy and later into the sound di which the letter represents to-day. This sound was already established in the language in words of Romance origin in which it was represented by g (e.g., in words such as gesture, ginger), and these words retain their spelling. J represents the same sound (di) in all' positions.
The minuscule form j is the lengthened form, retaining the dot, of minuscule i.