sixty-sixth

From sixty-six +‎ -th (ordinal suffix).

• IPA^(key): /ˌsɪksti ˈsɪk(s)θ/, /ˌsɪksti ˈsɪks/

sixty-sixth

1. The ordinal form of the number sixty-six, describing a person or thing in position number 66 of a sequence.

   The answer appears on the sixty-sixth page of the book.

   She finished sixty-sixth in the race.

   • 1912, Arthur Conan Doyle, The Lost World […], London; New York, N.Y.: Hodder and Stoughton, →OCLC:

     Though in his sixty-sixth year, I have never heard him express any dissatisfaction at the occasional hardships which we have had to encounter.

English ordinal numbers may function as either an adjective or as a noun, and almost never appear in the plural.

• 66th, 66^th

sixty-sixth (plural sixty-sixths)

1. One of sixty-six equal parts of a whole.

   A sixty-sixth of 1320 is 20.