Taw is the twenty-second and last letter of the Syriac abjad, with the numeral value four hundred, the highest that any single letter carries. It writes t and is the last of the six letters with hard and soft readings; soft taw is the voiceless th of English think. It joins only to the right.
Its name is the inherited Northwest Semitic word for a mark or a cross, and the older linear sign behind that name was in fact a cross-shaped mark, which makes taw one of the few letters whose name still describes something recognisable about its distant ancestor.
Taw also serves as the feminine ending of Syriac nouns, which a small dot written beside it can mark, so the letter closes an enormous number of words in the language. Between that grammatical ending and its position as the last letter of the alphabet, taw is a letter of endings in two different senses.
Figures above four hundred are written by combining letters or by marking one to multiply its value, since the alphabet supplies nothing higher. That limit is a property of having twenty-two letters, and it is shared by Hebrew and by the Arabic abjad order, both of which run out at the same place for the same reason.
Taw is one of the eight letters that do not join to the letter after them, so a word containing it is broken into more than one connected run, and a word ending in taw closes with a shape that stands clear of whatever follows. Its two readings, the hard t and the soft th, are governed by the same rule that governs the other five letters of that set, and running text ordinarily leaves the points that would settle it unwritten.