Siva vs Shiva

Siva and Shiva both are nouns.

Word	Noun	Adjective	Verb	Adverb
Siva	Yes	No	No	No
Shiva	Yes	No	No	No

As nouns, Siva and Shiva are synonyms defined as:

Siva and Shiva: the auspicious one; a major divinity in the later Hindu pantheon

Siva (noun)	Shiva (noun)
the auspicious one; a major divinity in the later Hindu pantheon	the auspicious one; a major divinity in the later Hindu pantheon