Arabic diacritics

Early written Arabic used only rasm (in black). Later, i‘jām (in red) were added so that letters such as ṣād (ص) and ḍād (ض) could be distinguished. Ḥarakāt (in blue)—which is used in the Qur'an but not in most written Arabic—indicate short vowels, long consonants, and some other vocalizations.
Arabic alphabet
Arabic script

The Arabic script has numerous diacritics, which include consonant pointing known as iʻjām (إِعْجَام), and supplementary diacritics known as tashkīl (تَشْكِيل). The latter include the vowel marks termed ḥarakāt (حَرَكَات; sg. حَرَكَة, ḥarakah).

The Arabic script is a modified abjad, where all letters are consonants, leading it up to the reader to fill in for vowel sounds. Short consonants and long vowels are represented by letters but short vowels and consonant length are not generally indicated in writing. Tashkīl is optional to represent missing vowels and consonant length. Modern Arabic is always written with the i‘jām—consonant pointing, but only religious texts, children's books and works for learners are written with the full tashkīl—vowel guides and consonant length. It is however not uncommon for authors to add diacritics to a word or letter when the grammatical case or the meaning is deemed otherwise ambiguous. In addition, classical works and historic documents rendered to the general public are often rendered with the full tashkīl, to compensate for the gap in understanding resulting from stylistic changes over the centuries.