The paper explored views in modern linguistic theories and Afghan linguist perspectives about essence of grammar, its original source, its function in language use and the relationship between mental rules and their description in grammar books. The data were collected from theoretical linguistics, grammar books and 10 Afghan professors who teach linguistics and Persian-Dari grammar in Kabul University via a questionnaire. MS excel was used to analyze the data. The results show the term Grammar refers to a set of constructional rules of a language located in speakers’ minds. It is unconscious knowledge which enables speakers of a language to produce and understand its utterances. These mental rules govern composition of phonemes, morphemes, words, phrases, clauses and sentences. Grammar books are like maps of original grammar which has mental essence and describe it. Children learn their native language from elders and their coeval speakers. Second language learners, can learn a foreign language through social interaction and grammar books. Compiling grammatical rules of a language introduces word formation techniques to expand its lexicon, help speakers to know more about their language capacities and possibilities. Grammar books aim to facilitate learning formal language, description of constructional rules, language learning for foreigners and provide correct writing guidelines. The research prescribes grammar teachers to use grammar as means of enrichment of formal language, as it can better function to do its scientific mission.

The aim of this study is to explore grammatical role of indefinite morpheme ‫ی‬ » -« in Persian attributive noun phrases and position of its use. Indefinite morpheme ‫ی‬ » -« is one of enclitics in Persian language.Enclitic is a kind of clitic. Clitic is a bound morpheme which is phonologically and semantically dependent on a host word. But syntactically it is like a free word, as it can be moved and displaced inside the sentence. Clitics are divided into two categories; proclitic and enclitic. Proclitic is added at the beginning of the host word, while enclitic is added at the end of it. Persian grammarians have two points of view regarding indefinite morpheme ‫ی‬ » -«. A group of them like Iran Kalbasi, Wida Sheqaqi and Mohammad Rasekh Mohand think that ‫ی‬ » -« is a clitic, while some of them like Khosraw Farshedward, Mohammad Ali Sorahi and Batol Alinajad say it is an affix. There are also different views about position of ‫ی‬ » -« in Attributive phrase (Noun + Adjective). A group of contemporary grammarians think that as a syntactic unit the position of enclitic ‫ی‬ » -« must be the end of the phrase and should be added to the adjective. Some others say that it can be added at the end of noun as well as at the end of adjective. The second group argues that in ancient literary works it is used in both styles.In this article the view of first group is supported by syntactic argumentations. The study has been implemented through a literature review having analytical-descriptive approach.