Introduction: The Persian language, though not belonging to the family of Semitic languages, has borrowed the heaviest from the Arabic language (Farshidvard: 1879: 39). A brief examination of Persian shows how heavily Persian is indebted to Arabic, but, as some scholars have pointed out, this has occurred mostly in the lexicon area as Persian has been affected very little in terms of syntax or grammar (Majd, 2011: 39). In addition to a great number of single lexical items, a number of grammatical morphemes have entered Persian. An example is the agreement of adjective and the noun it modifies in grammar in terms of gender, a characteristic which is peculiar to Arabic, and which was not common in the Dari Persian except in the sixth century AH, when Persian was heavily affected by Arabic. The first instance appeared in Aruzi’ s Chahar Maghaleh. Examples include: Moluk-e Maziyeh and Ghoroon Khaliyeh, etc. (Farshidvard, 1989: 23). Another instance of Arabic influence is the wide-spread adoption and usage of Arabic plural-making morphemes. Methodology: In Persian, the Arabic morpheme «-at» is sometimes used to pluralize Arabic and Persian words. Many Persian authorities frown upon this usage and argue that even Arabic words entering Persian should, as far as possible, also be pluralized using the plural morphemes «-ha» and «-in». Examples: Sokhanran enteghadhay-e (rather than enteghadat-e) ziyadi az chegoonegi-ye bargozariy-e marasem kard. [The lecturer made several criticisms of the way the ceremony was held]. However, a number of the Arabic plural forms have been established in Persian with certain words so much so that if the plural morphemes are changed the words sound unfamiliar and weird. Examples include: ettelaa’ aat; emkaanaat, enteshaaraat, etc. Besides, for certain nouns ending in «-at» such as adabiyaat, dokhaniyaat, amaliyaat, labaniyaat and maliyaat, there is no single form in Persian. The question to ask here is whether the Arabic plural marker «-at» in Persian has the same morphological, semantic, pragmatic and grammatical function as its counterpart in Arabic. Or is it different while sharing certain characteristics? Discussion: Contrary to what was initially believed that languages borrow just words from one another, the studies show that borrowing can occur in any part of language including phonemes, inflectional and derivational affixes, etc. However, borrowing words is more frequent than borrowing any other parts of the language. Although affixes can be borrowed, the common belief is that they are not directly borrowed but transferred indirectly from one language into another language. In other words, affixes, as part of the complex words, get transferred into another language. Theses affixes, as the borrowed words, can finally attach to the roots of the target language and produce hybrid words (Seifar, et. al, 2015). Recently, borrowing affixes have received remarkable attention and the focus in the published works has been on the way affixes are borrowed. There are two scenarios, direct and indirect, for the process of borrowing affixes (Winford, 2005: 385-409). The indirect borrowing has two stages. In the first stage, the speaker borrows some complex words from another language and uses them. In the second stage, probably a lot later, the speaker parses the blended words and finally the affixes are used with the roots in the receiving language and get generated. In the second scenario, the direct borrowing, once the borrowing takes place, the speaker, drawing on his own knowledge of the source language, identifies the affixes and attaches them to the roots of his own language and uses them. The main difference between these two scenarios lies in the whereabouts of the borrowed affix. Where has the speaker received the affix before combining it with the roots of his own language? From the source language complex words (indirect borrowing) or from his own knowledge of the source language? (direct borrowing). It seems that the indirect scenario best describes the phenomenon of affix borrowing. Paul (1891) maintains that words are borrowed as a whole; that is, derivative and inflectional affixes are not borrowed alone on their own part. However, if the many words that get transferred into another language have one certain affix, they can develop as easy as the target language words as a group and are possible to generate on their own. Thus, the received affix, by way of analogy, can attach to the target roots and later get generated (Paul, 1891: 469-470). Conclusion: One of the cases where Persian has been influenced by Arabic is the borrowing of Arabic plural morphemes including «-at». The plural morpheme entered Persian with certain Arabic plural nouns such as latamaat, majhoolat and mofradaat, but was later extended to pluralize originally Persian words such as baaghaat, gozareshaat and Shemiranaat, resulting in hybrid words. In terms of Phonetics, «-at» is no different in Persian than its usage in Arabic, but in terms of phonology, the only difference is in cases where «-at» has entered Persian directly as part of a loan word. A case in point is the loan word latamaat. In terms of phonology, «-at» follows Persian rather than Arabic phonological rules. For example, the Persian words are pluralized as ghazaliyaat and kashfiyaat while the plural forms of their Arabic counterparts are ghazaliyeh and kashfiyeh respectively. Also, the Persian word pand is pluralized as pandiyaat, quite against Arabic morphological rules. The plural marker «-at» is used for feminine nouns, whereas Persian lacks the feminine-masculine distinction. «-at» is not used in Persian to pluralize humans and animates and inanimate nouns are gender-neutral. In fact, «-at» is used in Persian to pluralize inanimate and abstract nouns that are gender-free. In terms of meaning, «-at» in Arabic indicates plural (three and more), whereas in Persian it indicates kind and group. Even though there are cases in Persian where this plural marker indicates plurality, this plurality meaning is mixed with the meanings of kind and group. This plural morpheme has undergone change in meaning and function, so that it is also clearly assumed a classifying function. Thus, we may speak of two types of «-at» one Arabic and one Persianized. The Arabic «-at» is the plural marker for feminine nouns, and the Persianized «-at» is the plural marker referring to groups. By group is meant a collection of things of various names but of the same nature. For example, shemiranat indicates a number of villages that are located in the same geographical area even though they have various names. Other examples include lavaasaanaat, noghaat as well as dahaat, baghaat and dastooraat. In fact. It may be said that this borrowed morpheme has assumed a merely morphological-grammatical function. Grammatical because it shows in some way the addition of a foreign plural-making element to the number of Persian plural-making markers. Morphological because it has assumed a derivative function in the word formation area. Also, it seems that in Persian, «Jat» is considered as a single morpheme and that sabzijaat no longer means sabzihaa; rather, various kinds of sabzi. On the other hand, words such as kompootjaat indicate the fact that what we do have here is not «-at», but «-Jat», which may be regarded as a form of the morpheme «-at». The question of the use of «-at» in Persian is a matter of debate. Generally, it is not approved as it is argued that the use of Persian plural markers is preferable. At first glance, this advice may seem warranted, specially because Persia has quite a lot of plural markers. A close look shows, however, that «-at» though originally Arabic has undergone such a deep change that it is not to be counted as Arabic any more as it is used based on Persian and not Arabic rules. Also, its usage has productively increased. Thus, we may claim with certainty that the single morpheme «-at» is a plural marker that Persian has borrowed indirectly from Arabic and that it is now a plural morpheme belonging to the Persian Language.