Our research sheds light on reconsidering the classification of parts of speech and addressing linguistic issues according to a sound grammatical vision stemming from two main axes: formal and functional, to keep pace with linguistic developments, organize their rules, remove ambiguity and suspicion, clarify the concept and confirm its truth, and avoid the disturbance of the old division, because each part of speech has an independent existence that shows its meaning and its grammatical, morphological and rhetorical effect on the sentence. Comparing the parts of speech in Arabic with the parts of speech in English according to the contrastive approach that compares two or more languages ​​to reveal the similarities and differences between the compared languages, and facilitates the process of learning a foreign language through the learner's mother tongue. The importance of our research stems from the importance of the topic of word division, and from the importance of both Arabic and English. Our research concludes that the similarities are more than the differences in the noun in both languages. This is the clearest evidence that there are common foundations among languages, that the Arabic language is not a novelty among world languages, and that this type of study is a serious attempt to facilitate learning a foreign language through the learner’s mother tongue. The points of difference indicate the flexibility and precision of the rules of the Arabic language, and its distinction from other constructed languages ​​such as the English language.