I, Is in English considered both as a vowel and consonant; though, since the vowel and consonant differ in their form as well as sound, they may be more properly accounted two letters.
I vowel has a long sound, as fine, thine, which is usually marked by an e final; and a short sound, as fin, thin. Prefixed to e it makes a diphthong of the same sound with the soft i, or double e, ee: thus field, yield, are spoken as feeld, yeeld; except friend, which is spoken frend. Subjoined to a or e it makes them long, as fail, neigh; and to o makes a mingled sound, which approaches more nearly to the true notion of a diphthong, or sound composed of the sounds of two vowels, than any other combination of vowels in the English tongue, as oil, coin. The sound of i before another i, and at the end of a word, is always expressed by y.
J consonant has invariably the same sound with that of g in giant; as jade, jet, jilt, jolt, just.