What does "ninth" mean?

Ninth: Constituting or being one of nine equal parts into which anything is divided.

Additional senses

  1. 2.The quotient of one divided by nine; one of nine equal parts of a thing; the next after the eighth.
  2. 3.(Mus.) (a) An interval containing an octave and a second. (b) A chord of the dominant seventh with the ninth added.

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