I stumbled upon this exchange so I hope you can help me. I'm writing a book of poetry, and I wanted to title it Starlight, but why use English, am I right? So I made the rookie error with Google translate and got inlustris, which I love only to find out it doesn't mean start light, but it still works on multiple levels. I'm just not sure which declination to use. Help?
The adjective "inlustris" is 3rd Declension. So for the title of a book of poems, you'd probably want a neuter plural nominative form, "Inlustria", as in "Carmina Inlustria" = "Illustrious Poems"
Note that you could also use the alternative spelling "ill-" instead of "inl-".
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