quenya_grammar1-10  Exercise 2: Nai siluvat elen atta
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  nai       wish particle, "may" (Chapter 8)
  siluvat   sil- "shine" + future -uva (Chapter 9) + dual -t (Chapters 3, 8)
  elen      star (Chapter 1)
  atta      two; numerals follow the noun (Chapter 6)
  = "May two stars shine."   (gloss as given on Wikipedia)

For "May one star shine": the dual -t would go (siluva), and the number would
change or disappear. These are built by rule; the page gives no such sentence.