1. I, the ninth letter of the English alphabet, takes its form from the Phœnician, through the Latin and the Greek. The Phœnician letter was probably of Egyptian origin. Its original value was nearly the same as that of the Italian I, or long e as in mete. Etymologically I is most closely related to e, y, j, g; as in dint, dent, beverage, L. bibere; E. kin, AS. cynn; E. thin, AS. þynne; E. dominion, donjon, dungeon. In English I has two principal vowel sounds: the long sound, as in pīne, īce; and the short sound, as in p&ibreve;n. It has also three other sounds: (a) That of e in term, as in thirst. (b) That of e in mete (in words of foreign origin), as in machine, pique, regime. (c) That of consonant y (in many words in which it precedes another vowel), as in bunion, million, filial, Christian, etc. It enters into several digraphs, as in fail, field, seize, feign. friend; and with o often forms a proper diphtong, as in oil, join, coin.
See Guide to Pronunciation, §§ 98-106.
The dot which we place over the small or lower case i dates only from the 14th century. The sounds of I and J were originally represented by the same character, and even after the introduction of the form J into English dictionaries, words containing these letters were, till a comparatively recent time, classed together.
2. In our old authors, I was often used for ay (or aye), yes, which is pronounced nearly like it.
3. As a numeral, I stands for 1, II for 2, etc.