Within Berber, it stands out for a number of unusual linguistic features, including the collapse of gender distinctions in the plural, the absence of dedicated negative forms of the verb, the use of full finite agreement on the verb in subject relativisation, the use of la for sentential negation and the borrowing from Arabic of a productive comparative form for adjectives.

Siwi also shows a typological feature that is strikingly rare, not only regionally but also worldwide: addressee agreement on demonstratives.

Siwi was traditionally associated with the Zenati subgroup of Berber, following the 15th century historian al-Maqrizi,[11] and Destaing,[12] who treated both as members of a "groupe du Nord", on the basis of similarities in the verbal system.

Demonstratives always follow adjectives or possessive suffixes, and may even follow relative clauses,[30] e.g.: akbərrobeə́nnəwmyaməllalwhitedawokthatakbər ə́nnəw aməllal dawokrobe my white that'that white robe of mine'Siwi nouns are specified for gender (masculine or feminine) and number (singular or plural; on the occasional occurrence of duals, see Numerical system below).

[31] Arabic loans often start with invariant (ə)l-, usually assimilating to a following coronal, e.g., ləqləm 'pen', ddhan 'oil'.

Unlike most larger Berber languages, Siwi has no state distinction: a noun takes the same form whether used as subject or as object.

[37] Siwi adjectives agree with their heads (or their referents) in gender and number, using a subset of the same affixes given above for nouns; for example:[38] However, agreement is not always complete.

Siwi is a pro-drop language, so the use of independent forms is relatively limited; instead, agreement markers or referential suffixes usually suffice to make pronominal reference unambiguous.

The verb 'open', for example, is conjugated in the perfective as follows:[49] In some cases, plural nouns trigger feminine singular agreement.

The basic stem is used in the imperative and in the irrealis/aorist; the latter normally takes a prefix ga- (preceding agreement suffixes), or (əd)da- for suggestives.

The imperfective is formed from the stem by a variety of morphological strategies, including gemination of the second consonant, t prefixation, and insertion of an a.

Among the relatively few materials published, four genres are conspicuous: song lyrics or poems, fairy tales, riddles, and proverbs.

[57] Malim[58] distinguishes songs, led by one man, from poems, shorter verse works recited antiphonally by groups at weddings; both are accompanied by the music of drums and horns.

In previous centuries these songs appear to have been of great symbolic importance to Siwi young men: a civil war in the oasis in 1712 was apparently terminated by a treaty including the stipulation that: The earliest Siwi lyrics to be published are those gathered by Bricchetti-Robetti;[60] others have been published in Jawharī[61] and Souag,[62] while Abd Allah[63] and Malim[64] provide several songs and poems in translation.

[70] Malim gives two Siwi folk tales ("The Green Cow" and "The King's Daughter and the Three Beautiful Girls") in English translation.

[72] Malim describes riddles as "once the preferred pastime of Siwi women", who would meet at night to exchange them, but notes that they have largely been superseded by watching television.

The thumbnail picture at the following link contains a list of pronouns and typical greetings first written in Siwi, then with the English pronunciation and translation, and ending with a description of the word in Arabic.