Nouns in Literary Arabic have three grammatical cases (nominative, accusative, and genitive (also used when the noun is governed by a preposition); three numbers (singular, dual and plural); two genders (masculine and feminine); and three “states” (indefinite, definite, and construct). The cases of singular nouns (other than those that end in long ā) are indicated by suffixed short vowels (/-u/ for nominative, /-a/ for accusative, /-i/ for genitive). The feminine singular is often marked by /-at/, which is reduced to /-ah/ or /-a/ before a pause. Plural is indicated either through endings (the sound plural) or internal modification (the broken plural). Definite nouns include all proper nouns, all nouns in “construct state” and all nouns which are prefixed by the definite article /al-/. Indefinite singular nouns (other than those that end in long ā) add a final /-n/ to the case-marking vowels, giving /-un/, /-an/ or /-in/ (which is also referred to as nunation).
Verbs in Literary Arabic are marked for person (first, second, or third), gender, and number. They are conjugated in two major paradigms (termed perfective and imperfective, or past and non-past); two voices (active and passive); and five moods in the imperfective (indicative, imperative, subjunctive, jussive and energetic). There are also two participles (active and passive) and a verbal noun, but no infinitive. As indicated by the differing terms for the two tense systems, there is some disagreement over whether the distinction between the two systems should be most accurately characterized as tense, aspect or a combination of the two. The perfective aspect is constructed using fused suffixes that combine person, number and gender in a single morpheme, while the imperfective aspect is constructed using a combination of prefixes (primarily encoding person) and suffixes (primarily encoding gender and number). The moods other than imperative are primarily marked by suffixes (/u/ for indicative, /a/ for subjunctive, no ending for jussive, /an/ for energetic). The imperative has the endings of the jussive but lacks any prefixes. The passive is marked through internal vowel changes. Plural forms for the verb are only used when the noun is not mentioned, and the feminine singular is used for all non-human plurals.
Adjectives in Literary Arabic are marked for case, number, gender and state, as for nouns. However, the plural of all non-human nouns is always followed by a singular feminine adjective, which takes the /-ah/ suffix.
Pronouns in Literary Arabic are marked for person, number and gender. There are two varieties, independent pronouns and enclitics. Enclitic pronouns are attached to the end of a verb, noun or preposition and indicate verbal and prepositional objects or possession of nouns. The first-person singular pronoun has a different enclitic form used for verbs (/-ni/) and for nouns or prepositions (/-ī/ after consonants, /-ya/ after vowels).
Nouns, verbs, pronouns and adjectives agree with each other in all respects. However, non-human plural nouns are grammatically considered to be feminine singular. Furthermore, a verb in a verb-initial sentence is marked as singular regardless of its semantic number when the subject of the verb is explicitly mentioned as a noun. Numerals between three and ten show “chiasmic” agreement, in that grammatically masculine numerals have feminine marking and vice-versa.
The spoken dialects have lost the case distinctions and make only limited use of the dual (it occurs only on nouns and its use is no longer required in all circumstances). They have lost the mood distinctions other than imperative, but many have since gained new moods through the use of prefixes (most often /bi-/ for indicative vs. unmarked subjunctive). They have also mostly lost the indefinite “nunation” and the internal passive. Modern Standard Arabic maintains the grammatical distinctions of Literary Arabic except that the energetic mood is almost never used; in addition, Modern Standard Arabic sometimes drop the final short vowels that indicate case and mood.
As in many other Semitic languages, Arabic verb formation is based on a (usually) triconsonantal root, which is not a word in itself but contains the semantic core. The consonants k-t-b, for example, indicate ‘write’, q-r-ʾ indicate ‘read’, ʾ-k-l indicate ‘eat’, etc. Words are formed by supplying the root with a vowel structure and with affixes. (Traditionally, Arabic grammarians have used the root f-ʿ-l ‘do’ as a template to discuss word formation.) From any particular root, up to ten different verbs can be formed, each with its own template; these are referred to as “form I”, “form II”, … up through “form X”. These forms, and their associated participles and verbal nouns, are the primary means of forming vocabulary in Arabic.