Arab and non-Arab grammarians have been interested in studying the noun since ancient times due to its great importance and great benefit in constructing the sentence and conveying the speech. Therefore, our study dealt with the noun in the three languages: Arabic, English and Persian; to show the nature of the noun alone, its characteristics that distinguish it from the rest of the parts of speech, its representation, its parsing, and what it forms of a sentence, and to stand on the similarities and differences in the noun between the three languages. The best way to suit such a study is the comparative approach that compares different languages. We chose to compare Arabic with English and Persian; since these three languages ​​are global languages, united in characteristics and different in characteristics. The importance of the research is clear in its comparative study of global languages: Arabic, English and Persian, to facilitate learning a foreign language in the mother tongue, and master the translation of foreign languages. It aims to contribute seriously and effectively to the development of academic materials in teaching foreign languages ​​by clarifying the similarities, differences and compatibility between languages, narrowing the problems for learners, identifying difficulties and facilitating their learning. The results proved that there are more similarities than differences in the noun in the three languages. This means that the Arabic language is not an innovation among the world languages, and that there are common basics among the languages. As for the differences, they reveal the strength and precision of the Arabic language and the importance of grammar in it.