Arabic is the language of the Qurʾān (or Koran, the sacred book of Islam) and the religious language of all Muslims. Literary Arabic, usually called Classical Arabic, is essentially the form of the language found in the Qurʾān, with some modifications necessary for its use in modern times; it is uniform throughout the Arab world. Colloquial Arabic includes numerous spoken dialects, some of which are mutually unintelligible. The chief dialect groups are those of Arabia, Iraq, Syria, Egypt, and North Africa. With the exception of the dialect of Algeria, all Arabic dialects have been strongly influenced by the literary language.

The sound system of Arabic is very different from that of English and the other languages of Europe. It includes a number of distinctive guttural sounds (pharyngeal and uvular fricatives) and a series of velarized consonants (pronounced with accompanying constriction of the pharynx and raising of the back of the tongue). There are three short and three long vowels (/a/, /i/, /u/ and /ā/, /ī/, /ū/). Arabic words always start with a single consonant followed by a vowel, and long vowels are rarely followed by more than a single consonant. Clusters containing more than two consonants do not occur in the language.

Arabic shows the fullest development of typical Semitic (Semitic languages) word structure. An Arabic word is composed of two parts: (1) the root, which generally consists of three consonants and provides the basic lexical meaning of the word, and (2) the pattern, which consists of vowels and gives grammatical meaning to the word. Thus, the root /k-t-b/ combined with the pattern /-i-ā-/ gives kitāb ‘book,' whereas the same root combined with the pattern /-ā-i-/ gives kātib ‘one who writes' or ‘clerk.' The language also makes use of prefixes and suffixes, which act as subject markers, pronouns, prepositions, and the definite article.

Verbs in Arabic are regular in conjugation. There are two tenses: the perfect, formed by the addition of suffixes, which is often used to express past time; and the imperfect, formed by the addition of prefixes and sometimes containing suffixes indicating number and gender, which is often used for expressing present or future time. In addition to the two tenses, there are imperative forms, an active participle, a passive participle, and a verbal noun. Verbs are inflected for three persons, three numbers (singular, dual, plural), and two genders. In Classical Arabic there is no dual form and no gender differentiation in the first person, and the modern dialects have lost all dual forms. The Classical language also has forms for the passive voice.

There are three cases (nominative, genitive, and accusative) in the declensional system of Classical Arabic nouns; however, nouns are no longer declined in the modern dialects. Pronouns occur both as suffixes and as independent words.