بَعْدُ

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

الْبَعْدُ 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

الْبَعْدُ loses it’s definite article, changing to بَعْدُ due to it being a possessed noun

when used as an adverb is undeclinable: Afterwards, Again

To be far off, go a long way off, go away, die, perish

Surah/Below are the 4 verses in the holy Quran containing the possessed nounبَعْدُ
Verse
Allah (SWT) said, “Indeed, I will send it down to you but whoever among you disbelieves thereafterقَالَ اللهُ إِنِّي مُنَزِّلُهَا عَلَيْكُمْ فَمَنْ يَكْفُرْ بَعْدُ مِنْكُمْ
5-115then truly I will punish him with a punishment the like of which I have not punished any other in the creationفَإِنِّي أُعَذِّبُهُ عَذَابًا لَّآ أُعَذِّبُهُ أَحَدًا مِنَ العَالَمِيْنَ
1
26-120
47-4
95-7So, what makes you deny the final judgement?فَمَا يُكَذِّبُكَ بَعْدُ بِالدِّيْنِ