Encyclopædia Britannica, Ninth Edition/T

 T is the twentieth symbol in our alphabet. It has varied but little in form since the earliest days when it appeared in Greece and Italy, though some of the Italic alphabets exhibit variants: e.g. in Umbrian and Etruscan inscriptions we find the horizontal stroke sometimes on one side only, and slanting; sometimes the form is nearly that of our ordinary small t without the ornamental turn at the bottom. In value it has been in all languages a surd or voiceless dental, corresponding to d, which is voiced. But the term "dental" includes some varieties of position, of which the most definite are—(1) where the point of the tongue touches the teeth (true "dental"), as in French; (2) where the tongue touches the gum behind the teeth, and not the teeth at all, as in English; (3) where the point of the tongue is slightly bent back against the palate, producing the sound much heard in south India (often called "cerebral"). T when followed by I or y is liable to pass into the s-sound; this happened in the local dialects of Italy before the Christian era; at Rome the transition was later. This changed sound passed on into the Romance languages, e.g. in French "nation," pronounced "nasion," whence in England it was sounded first as "nasiun" and now as "nashun." Similarly in English t followed by u undergoes a change of sound; this is due, however, to the old sound of ū viz., long French u, or Old English y. This long yy developed into theiu sound heard in "use," "cure," &c.; then the new I affected the preceding tand the result is tsh as in "nature" (natshure); similarly d in "verdure" is sounded as dzh (verdzhure).

English employs the digraph th to denote two sounds, differing as voiceless and voiced sounds - the initial sounds of "thin" and "then" respectively. It would be a great convenience if dh could be used for the voiced sound, so that "then" should be written "dhen," But it would be even better if the single symbols could be employed to denote these single sounds, as was to some extent the case in the earlier days of our language: in Anglo-Saxon we have the two symbols ᛟ and ᚦ. The first is only a d crossed; the second was a rune and was called "thorn." These, however, were not consistently employed one for the voiceless and one for the voiced sound; also th is actually found in the oldest texts, and later on it occurs together with ᛟ and ᚦ. It is probable that the voiceless sound was originally the only one in Teutonic. It was eventually differentiated into two sounds; but, as is usually the case, writing remained more archaic than speech. In modern English and Icelandic, and probably in the parent Teutonic also, initial th is voiceless, except in English in a small number of pronouns and particles in common use, as "thou," "this," "that," "then," "than," "though," "thus"; and it is regularly voiceless when final. The nature of the two sounds is this: the tongue is pressed against the back of the teeth (sometimes, especially when used by foreigners, against the bottom of the upper teeth) and either the breath for th or the voice for dh is forced through the interstices of the teeth. This pair of sounds is found in modern Greek, where th appears as θ and dh as δ. In Spanish and in Danish under certain circumstances the sound denoted by d is dh.