or PORCUPINE, a genus of quadrupeds belonging to the order of glires. See MAMMALIA Index. I, or i, the ninth letter and third vowel of the alphabet, is pronounced by throwing the breath suddenly against the palate, as it comes out of the larynx with a small hollowing of the tongue, and nearly the same opening of the lips as in pronouncing a or e. Its sound varies: in some words it is long, as high, mind, &c.; in others short, as bid, hid, fin, &c.; in others, again, it is pronounced like y, as in collier, onion, &c.; and in a few, it sounds like ee, as in machine, magazine, &c. No English word ends in i, e being either added to it, or else the i turned into y.

But besides the vowel there is the jod consonant; which because of its different pronunciation, has likewise a different form, thus J, j. In English, it has the soft sound of g; nor is it used, but when g soft is required before vowels, where g is usually hard: thus we say, jack, jet, join, &c. instead of gack, get, gain, &c. which would be contrary to the genius of the English language.

I, used as a numeral, signifies one, and stands for so many units as it is repeated times; thus I, one; II, two; III, three, &c.; and when put before a higher numeral, it subtracts itself, as IV, four, IX, nine, &c. But, when set after it, so many are added to the higher numeral as there are I's added: thus VI is $5+1$, or six; VII, $5+2$, or seven; VIII, $5+3$, or eight. The ancient Romans likewise used IO for 500, CIO for 1000, IOC for 5000, CCICIO for 10,000. Farther than this, as Pliny observes, they did not go in their notation; but when necessary repeated the last number, as CCCICIO, CCCICIO for 200,000; CCCICIO, CCCICIO, CCCICIO, for 300,000; and so on.

The ancients sometimes changed i into u; decimus for decimus; maximus for maximus, &c.

According to Plato, the vowel i is proper to express delicate but humble things, as in this verse in Virgil which abounds in i's, and is generally admired:

Accipiant inimicum imbrem, rimisque satiscunt.

I, used as an abbreviation, is often substituted for the whole word JESUS, of which it is the first letter.