Declension table of ?śāśvatatva

Neuter	Singular	Dual	Plural
Nominative	śāśvatatvam	śāśvatatve	śāśvatatvāni
Vocative	śāśvatatva	śāśvatatve	śāśvatatvāni
Accusative	śāśvatatvam	śāśvatatve	śāśvatatvāni
Instrumental	śāśvatatvena	śāśvatatvābhyām	śāśvatatvaiḥ
Dative	śāśvatatvāya	śāśvatatvābhyām	śāśvatatvebhyaḥ
Ablative	śāśvatatvāt	śāśvatatvābhyām	śāśvatatvebhyaḥ
Genitive	śāśvatatvasya	śāśvatatvayoḥ	śāśvatatvānām
Locative	śāśvatatve	śāśvatatvayoḥ	śāśvatatveṣu

Compound śāśvatatva -

Adverb -śāśvatatvam -śāśvatatvāt