Scripts used for writing by the Syriac Christians from the 1st century ad until about the 14th century. Using a Semitic alphabet, it is descendent Aramaic cursive with 22 letters, all representing consonants, and was typically written from right to left, although occasionally vertically downward. Diacritical marks used to represent vowels were introduced in the 8th century and two systems of vocalization were developed, one similar to the system in Arabic, and one using small Greek letters above or below the line.