The I, 9th letter of the Latin and of most other European alphabets, derived from the 10th Phoenician, Hebrew, etc, where it is named yod (Heb. yad, hand), and considered as a consonant. A dot under other consonants denotes its vocality in the Hebrew, and other marks in the other Semitic languages. It is the 11th letter in Armenian, the 28th and last in Arabic, and the 32d and last in Persian and Turkish. The Greek' is the 9th letter, but 10th numeral sign, and is sometimes subscribed to three vowels, thus, The sound of this letter is the highest in the vocal scale, the counterpart of that of U (oo). This sound (not as pronounced in mine, but as in pique or pin) is symbolic, in many words of all languages, of what is little, thin, slim, swift, shrill, light, flitting; this property is mentioned by Plato. It is uttered through a broad but very thin interstice, which the tongue leaves between itself and the hard palate by being closely raised toward it and pressed against the molar teeth, while the larynx is raised higher than in the formation of any other vocal. Hence it is considered as a palatal by John Wallis, and as a dental by 0. Amman. Modern Greeks pronounce n, ei, oi, v, and vi like i; whereas the ancients made at, el, ol, and vl diphthongal, giving to the v a sound like that of the German u, and to the n that of German a. The Romans used I both as a vowel and as a consonant; since they, as well as the Egyptians, Hebrews, and Greeks, knew no such sounds as the French and English give to J (zh and dzh). The Italian language is impaired in its beauty by the frequency of I in its grammatic formations. In Italian it is also used for softening the pronunciation of c, g, and sc.
In Spanish manuscripts an initial I is always written Y, for which I is substituted in printing except where it has the consonant sound, as in yerba. In English the diphthongal sound in mine (Ger. mein) is taken for the long sound of I, and its genuine long sound is transferred to E, as in mete. The latter sound, long and short, is written in many different ways, some only in single words; as in be, lee, sea, people, key, coecal, foetus, seize, mien, marine; pin, sieve, forfeit, build, lynx, women, busy, tortoise. Its English long sound is written in 10 ways, as in mile, aisle, lie, height, guide, my, ay, eye, buy, rye. In many words, like bird, stir, I has the sound of U in fur. The consonantal sound of I is represented by J in Italian and in German and other Teutonic languages, and by Y in French, Spanish, Portuguese, English, etc. (See J, and Y.) It was formerly the practice to class words in I and J together in dictionaries and other alphabetical works; but this is now nearly abandoned in all languages. - In Latin abbreviations, I stands for invictus, in, inferi, Iulius, Junius, etc.; I. C. for iuris consultus, etc.
During the lethargy of literature I was used to denote 100; but in the Roman numeration it stands for 1. When placed before another numeral it is subtracted, and when following is added; as IV, 4; VI, 6. On French coins it denotes Limoges as the place of coinage. - In music, I is the name of the 9th tie on the neck of the lute and of various old musical instruments. Kirnberger, Fasch, and other organists denoted by it a by-tone between a sharp and b flat.