Declension table of ?dīrghatva

Neuter	Singular	Dual	Plural
Nominative	dīrghatvam	dīrghatve	dīrghatvāni
Vocative	dīrghatva	dīrghatve	dīrghatvāni
Accusative	dīrghatvam	dīrghatve	dīrghatvāni
Instrumental	dīrghatvena	dīrghatvābhyām	dīrghatvaiḥ
Dative	dīrghatvāya	dīrghatvābhyām	dīrghatvebhyaḥ
Ablative	dīrghatvāt	dīrghatvābhyām	dīrghatvebhyaḥ
Genitive	dīrghatvasya	dīrghatvayoḥ	dīrghatvānām
Locative	dīrghatve	dīrghatvayoḥ	dīrghatveṣu

Compound dīrghatva -

Adverb -dīrghatvam -dīrghatvāt