20th letter and 16th consonant of , the English and other alphabets derived from the Roman, the 19th of the Greek (tau), and the 9th of the Hebrew (teth). It is of the denti-lingual class, and represents the sound produced by a forcible emission of the breath after placing the tongue against the roof of the mouth near the roots of the teeth. This forcible emission of the breath is the principal distinction between the sounds of t and its sonorous counterpart d. In etymology it is interchangeable with d, and sometimes with th, p, s, and l. By itself it has but one sound; but combined with h, it forms a simple sound, hard or soft in quality, distinct from that of either component; as the th in thigh, which the Anglo-Saxons represented by 8, the Greeks by θ (theta), and the Hebrews by (tav); or as in thy, which the Anglo-Saxons represented by ž. This sound is wanting in all the other European languages except Spanish (d, z, and c before e or i), modern Greek (θ and δ), Danish (d between vowels, very faint), and Welsh (dd). In French t is dropped in many words from the Latin where it is preceded and followed by a vowel; as in pere, mere, vie, from pater, mater, vita ; also from the termination of many words.
In English, before i and another vowel, t has the sound of sh, as in nation ; in French, of s ; in German, of tz - As a Greek numeral r stood for 300, ,τ for 300,000. Among the Latins T represented 160, and with a dash above it (τ) 160,000. As an abbreviation it stands for the-ologia, as in S. T. D., sacroe theologioe doctor; and in ancient writings, monuments, or coins, for Titus, Titius, Tullius, and sometimes tri-bunus. (See D).