The third day of the week, as it was named by the Shire-hobbits at the end of the Third Age. The similarity to our own modern 'Monday' is not coincidental: both are days originally dedicated to the Moon. The form used in the Shire dated back to an original Common Speech form Monendei. That old form was itself a translation of the original Elvish day-name, which was Isilya in Quenya, or Orithil in Sindarin.