Ta is the third letter of the modern Arabic order, written as the shared bowl skeleton with two dots above. In the older abjad order it stands far later, at the twenty-second place, and carries the numeral value four hundred. The distance between its two positions is a useful reminder that the Arabic alphabet has two orders in simultaneous use: one arranged by shape, which is how the letters are taught and how dictionaries are built, and one inherited from the older Semitic sequence, which is retained for numbers, for chronograms, and for the ordering of certain traditional lists.
Ta joins on both sides and reduces to a dotted tooth at the beginning and in the middle of a word. It is a sun letter, so the lam of the definite article assimilates to it and is not heard, the resulting doubling being marked in fully pointed text by a shadda written over the ta.
Arabic also writes a second, bound form of the letter, ta marbuta, which is not counted among the twenty-eight. It closes most feminine singular nouns and is drawn as a ha carrying the two dots of ta, a compromise shape that reflects a compromise pronunciation: it is sounded as t when the word carries its case ending and as a light h, or as nothing at all, when the word is pronounced in pause. The name of the letter descends from the Northwest Semitic tav, whose sense was mark, and it is the cognate of Hebrew tav and Syriac taw.