There is one Arabic Grammar, it's the official or the formal way to communicate, you can find this on TV, Newspaper, some official speeches, Books,..., and every Arab country has a different dialect, for example : "Moroccan Arabic is foreign to Levantines, while Iraqi can be quite a puzzle for Egyptians." (Michael Erdman) So yes for dialects we are different, but for "Arabic Fusha (the formal language)", it's the language that we study at the school, and its grammar. you can check this article to have an idea. http://www.slate.com/blogs/lexicon_valley/2014/09/22/arabic_diglossia_the_many_varieties_of_what_s_popularly_considered_a_single.html

Shahin, Please read this article http://www.italki.com/article/285/arabic-some-advice-for-beginners#.VOmmyeaUeJo

This is a point of contention, and a somewhat emotional one at that, but there are substantial disparities between the various varieties of Arabic both in lexis and in grammar. Testament to this is the fact that all varieties of Arabic are not mutually intelligible with one another. Ethnologue classifies Egyptian Arabic, for example, as a distinct language in its own right. The distinctions are too numerous to list. MSA for "death" (موت) is /mawt/, but in Iraqi it's /mu:t/. MSA for "I speak Arabic" is "`ana `atakallam al-3arabiya," but in Lebanese one would say, "`ana be7ki 3arabi." If you're not interested in any specific subregion per se, do the obvious thing to do and go for MSA, which is the lingua franca and the oft-preferred mode of communication in formal settings. Command of the language is not, however, quite universal in the Arabic-speaking world, especially in some countries. If you only know MSA, you will find it difficult or impossible to understand what is being said on the streets.

As a student of Arabic, I do think the grammar is somewhat different between dialects and formal MSA. For example, in MSA you will say: "hadhal-walad" (this boy), but in Egyptian you change the order of the words -- al-walad da. Also, some levantine dialects use "sh" for negation, like the Lebanese and Palestinians, and some (like Syrians) are not ("b'3refesh" vs. "ma b'3ref" or "mush" vs. "mu" etc.). Lebanese and Syrians use the word "3am" for present progressive, other dialects don't. As for the african dialects, I don't know much, but I do know that some conjugations are different. For example in most dialects (and MSA) the word "n'akol" is "we will eat". In morocco it's "I will eat" (and then there's also a difference in the pronoun "we"). In short - there are differences no doubt. That being said, the rational of the language, the basic grammar, the way one structure a sentence -- these are all very similar in all dialects of arabic.

Arabs have diff. dialects but the grammar is the same you can find this in all arabs books or tv that's back to the inventor of grammar in Arabic is one of the biggest scientists in Arab history "Abu al-Aswad al-Du'ali" And completed his way other scientists after him. so all arabs have same grammar