ruinis
ruinis is a Latin form of ruina, meaning “fall, collapse; ruin, destruction; (pl.) ruins”. It is the ablative plural feminine noun or dative plural feminine noun.
Found 74 times in the Latin texts on Socratos.
Where it is used
Cicero, Letters to his Friends 5.17.1: … termissione consuetudinis meae superioribus temporibus ad te nullas litteras misi, sed quod priora tempora in ruinis rei p. nostrisque iacuerunt, posteriora autem me a scribendo tuis iniustissimis atque acerbissimis incommodis …
All forms of ruina (declension table)
Source: Socratos (socratos.org), a free reader for Ancient Greek and Latin. Grammar from the Perseus Treebank and Morpheus; dictionary entries from Lewis & Short, A Latin Dictionary (Perseus Digital Library, CC BY-SA). Counts are from the texts on Socratos.