The Shiva Purana bzw. Shaiva Purana or Shiva Mahapurana belongs to the 18 big Puranas.
The mythical author is Veda Vyasa.
The Purana consists of 24.000 shlokas, which are divided into 6(7) Samhitas or sections, which are again subdivided into chapters (adhyaya).
Samhitas include, besides (also allegorical) narratives extensive comments on yoga and mantras. The most famous mantra is here the OM NAMAHA SHIVAYA.
According to a passage in a version of the Vidyeśvara - Saṁhitā and of the Vāyaviya - Saṁhitā had the Shiva-Purana originally 12 Samhitas
(Vidyeshvara Samhita - 10,000 Verses ; Rudra Samhita - 8,000 Verses ; Vainayaka Samhita - 8,000 Verses; Uma Samhita - 8,000 Verses; Matri Samhita - 8,000 Verses ;Rudraikadasha Samhita - 13,000 Verses ; Kailasa Samhita - 6,000 Verses ; Shatarudra Samhita - 3,000 Verses ; - Sahasrakotirudra Samhita - 11,000 Verses ; Kotirudra Samhita - 9,000 Verses ; Vayaviya Samhita - 4,000 Verses ; Verse ; Dharma Samhita - 12,000 Verses, of which 5 were shortened.
The entire group of twelve Samhitas included once about a hundred thousand slokas. Five Samhitas were deleted in the course of the reconstruction and reduction of Puranas.
Today's 6 Samhitas are : Jnana samhita(78 chapters), vidyeshvara samhita(16 chapters), Kailasa samhita(12 chapters), Sanatkumar samhita (59 chapters), Vayaviya samhita(59 chapters) und Dharma samhita(65 chapters).
Sometimes 7 Maha-Samhitas with different names are enumerated as well : Vidyeshvar Samhita, Rudra Samhita, Shatrudra Samhita, Koti Rudra Samhita, Uma Samhita, Kailash Samhita, Vayviya Samhita.
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