حَيَاتِ

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

الحَيَاتُ is the natural state of this definite noun and it becomes الحَيَاتِ 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

الحَيَاتِ loses it’s definite article, becoming حَيَاتِ due to it being a possessed noun

Life

To live, be alive, be ashamed, spend (the night) awake, fertilize the earth, keep anyone alive; spare any one, let anyone alive, remove prudency, modesty and shamefulness, make immodest

مَعْرِفَةٌمُفْرَدٌمُؤَنَّثٌمَجْرُوْرٌح ي يبَاب سَمِعَفَعَلَةٌحَيِيَ يَحْيَااسْمٌاِسْمُ الجِنْسِ
DefiniteSingularFeminineGenitiveRootLifePatternسNounGeneric or common Noun
Surah/Below are the 2 verses in the holy Quran containing the possessed nounحَيَاتِ
Verse 
46-20
89-24He will say “Alas would that I had sent forth (good deeds) for my life (hereafter)يَقُوْلُ يَالَيْتَنِى قَدَّمْتُ لِحَيَاتِى