علم النحو    (Ilm-un-Nahw) is the Arabic term for the science of grammar, specifically focusing on the rules of sentence construction and the inflection of words in the Arabic language. It deals with how words combine to form meaningful phrases and sentences, and how their forms change based on their grammatical function. 

Here's a more detailed explanation:

What it covers:

Sentence Structure:

Nahw dictates how words are arranged in a sentence to create proper syntax and meaning according to Oxford Reference. 

Word Inflections:

It explains how the endings of words (especially nouns and verbs) change to indicate grammatical roles like subject, object, etc. 

Grammatical States (I'rab):

Nahw also covers the concept of grammatical states, which are the different forms a word can take based on its function in a sentence. Understanding these states is crucial for accurate interpretation of Arabic text. 

Why it's important:

Understanding the Quran and Hadith: Ilm-un-Nahw is considered essential for understanding the Quran and the Hadith (sayings and actions of the Prophet Muhammad). 

Accurate Communication: Mastering Nahw enables accurate and clear communication in Arabic. 

Foundation for other Islamic Sciences: It's a foundational science for other disciplines like Tafsir (Quranic exegesis) and Fiqh (Islamic jurisprudence). 

In essence, Ilm-un-Nahw is the study of how Arabic words combine to form meaningful and grammatically correct sentences, and how their forms change based on their role in the sentence. says a post on the website aalequtub.com It's a crucial element for anyone seeking to learn and understand the Arabic language, especially for those studying Islamic texts.