الأَمِيْنِ

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

الأَمِيْنُ is the natural state of this definite noun and it changes to الأَمِيْنِ due to: 1) a preposition that precedes it or 2) a possessed noun that precedes it or 3) it’s a noun of dependent declension a) نَعْتٌ / صِفَطٌ adjectives b) التَّوْكِيْدُ emphatic c) المَعْطُوْفٌ conjunction d) البَدَلُ synonym

Trustworthy, Faithful, Steadfast

To trust, be secure, be in safety, confine in

Verse/Below is the only verse in the holy Quran containing the genitive nounالأَمِيْنِ
Ayat
95-3and this secure cityوَهَذَا الْبَلَدِ الأَمِيْنِ