Declension table of ?upānayana

Neuter	Singular	Dual	Plural
Nominative	upānayanam	upānayane	upānayanāni
Vocative	upānayana	upānayane	upānayanāni
Accusative	upānayanam	upānayane	upānayanāni
Instrumental	upānayanena	upānayanābhyām	upānayanaiḥ
Dative	upānayanāya	upānayanābhyām	upānayanebhyaḥ
Ablative	upānayanāt	upānayanābhyām	upānayanebhyaḥ
Genitive	upānayanasya	upānayanayoḥ	upānayanānām
Locative	upānayane	upānayanayoḥ	upānayaneṣu

Compound upānayana -

Adverb -upānayanam -upānayanāt