الصَّخْرَ

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

الصَّخْرُ is the natural state of this definite noun and becomes الصَّخْرَ 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

Rocks

To be rocky (place)

مَعْرِفَةٌجَمْعٌمُذَكَّرٌمَنْصُوْبٌص خ ربَاب سَمِعَفَعْلٌصَخِرَ يَصْخَرُاسْمٌاِسْمُ الجِنْسِ
DefinitePluralMasculineAccusativeRootRocksPatternسNounGeneric or common noun
Surah/Below is the only verse in the holy Quran containing the nounالصَّخْرَ
Verse 
89-9and Thamud who hewed out rocks in the valleyوَثَمُوْدَ الَّذِيْنَ جَابُوْا الصَّخْرَ بِالْوَادِ