النَّجْدَيْنِ

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

النَّجْدَانِ is the natural state of this definite noun and becomes النَّجْدِيْنِ due to it being the: 1) المَفْعُوْلُ بِهِ object of a verb or 2) اسْمُ of إِنَّ or 3) خَبَرُ of كَانَ or 4) المَفْعُوْلُ فِيْهِ adverb of time or place or 5) المَفْعُوْلُ لَهُ noun that gives the reason for doing a thing or 6) المَفْعُوْلُ مَعَهُ noun that comes after the و which means “along with” or 7) المَفْعُوْلُ المُطْلَقُ is the مَصْدَرٌ of the verb occurring in the sentence or 8) الحَالُ adverb of manner or 9) التَّمْيِيْزُ noun that specifies the meaning of a vague word or 10) المُسْتَثْنَى noun that comes after إِلَّا meaning “except” or 11) المُنَادَى noun of calling

Two ways

To overcome prevail over, become manifest

Surah/Below is the only verse in the holy Quran containing the indefinite, accusative nounالنَّجْدَيْنِ
Verse 
90-10and shown him the two waysوَهَدَيْنَاهُ النَّجْدَيْنِ