The focal point of this paper is to make a modern approach to the classification of Arabic sentences. To get to this point, this paper will first look at the definition and classification method of the sentence by traditional Arab grammarians, and then try to determine it`s theoretical efficiency in terms of modern linguistics. As far the definition of the sentence, it`ll be focused on the use of two terminologies, al-jumlah and al-kal?m and the difference criteria between them. The earlier Arab grammarian such as Ibn Jinni used al-jumlah as the same concept of al-kal?m, pointing out that al-kal?m is an independent form of speech to convey the full meaning. Ibn Jinni has defined al-jumlah (sentence) by both syntactic and semantic criteria. On the other hand, Ibn Hish?m adopted another criteria to define the sentence. He defined the sentence by just syntactic criteria, saying that the sentence is a structure consisted of subject and predicate regardless of the independence of the structure. He tended not to differentiate sentences and clauses. It will be followed by the classification method of the sentence. In this part, this paper will deal with two types of the classification method, 1) the classification by way of the word order by which nominal sentence and verbal sentence are classified, 2) the classification according to the desinential inflection of the sentence. The latter method premises that the sentence replaces the word. To classify nominal sentence and verbal sentence, this paper will investigate the functional characteristics of the subject(al-mubtada?) of nominal sentence, compared with the subject(al-f??il) of verbal sentence. Especially, the paper will focus on the head-first parameter in Arabic sentence which makes the subject of verbal sentence different from the subject of nominal sentence. In addition, it will make a modern approach to the functional independence of the subject of nominal sentence from the vocal governors within the predicate, prescribing that the subject of nominal sentence is located in the non-argument position and thus is needed to have a semantical relations with the resumptive pronoun in the predicate. Finally, this paper will give an evidence of the empty pronoun as a subject of the adjective by way of the classification according to the desinential inflection of the sentence.