الصَّيْفِ

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

الصَّيْفُ is the natural state of a definite noun and it changes to الصَّيْفِ 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

Summer

To pass the summer

Grammatical analysis of الصَّيْفِ
اسْمٌ مَجْرُوْرٌ بِالكَسْرَةِ الزَّاهِرَةِ
مَعْرِفَةٌمُفْرَدٌمُذَكَّرٌمَجْرُوْرٌص ي فبَابٌ ضَرَبَفَعْلٌصَافَ يَصِيْفُاسْمٌاسْمُ الجِنْسِ
DefiniteSingularMasculineGenitiveRootSummerPatternضNounCommon noun
Surah/Below is the only verse in the holy Quran consisting of the possessive nounالصَّيْفِ
Verse
106-2Their familiarity with the journey of winter and summerإِيْلَافِهِمْ رِحْلَةَ الشِّتَآءِ وَالْصَّيْفِ