نَارُ

A word in the Arabic language will either be 1) a verb or 2) a noun or 3) a particle – نَارُ is a noun

A noun may either be 1) Definite or indefinite 2) Masculine or feminine 3) Singular, dual or plural 4) Nominative, accusative or genitive

النَّارُ is the natural state of this definite noun and it is in this state ( مَرْفُوْعٌ) when the noun is: 1) the subject المُبْتَدَأُ or 2) the predicate الخَبَرُ or 3) اسْمُ كَانَ or 4) خَبَرُ إِنَّ or 5) الفَاعِلُ subject of a verb in the active voice or 6) نَائِبُ الفَاعِلِ subject of a verb in the passive voice or 7) it’s a noun of dependent declension a) نَعْتٌ / صِفَطٌ adjectives b) التَّوْكِيْدُ emphatic c) المَعْطُوْفٌ conjunction d) البَدَلُ synonym

النَّارُ loses it’s definite article, changing to نَارُ due to it being a possessed noun

Fire, burning flame, heat, war

To emit fire or light, shine, sparkle, irritate, vex or provoke war, create heat

Surah/Below are the 4 verses in the holy Quran containing the nominative, possessed nounنَارُ
Verse
Those who remained behind rejoiced in their staying behind the Messenger of Allah (SWT)فَرِحَ المُخَلَّفُوْنَ بِمَقْعَدِهِمْ خِلَافَ رَسُوْلِ اللهِ
and they disliked striving with their wealth and their lives in the way of Allah (SWT)وَكَرِهُوا أَنْ يُجَاهِدُوا بِأَمْوَالِهِمْ وَأَنْفُسِهِمْ فِي سَبِيْلِ اللهِ
and they said, “Do not go forth in the heat” say, “the fire of hell is a more intense heat”وَقَالُوا لَا تَنْفِرُوا فِي الحَرِّ قُلْ نَارُ جَهَنَّمَ أَشَدُّ حَرًّا
9-81if only they could understandلَّوْ كَانُوا يَفْقَهُوْنَ
21-69
35-36
104-6The kindled fire of Allah (SWT)نَارُ اللهِ الْمُوْقَدَةُ