\Nine"teenth`\, a. [Cf. AS. nigonte['o]?a.]
1. Following the eighteenth and preceding the twentieth;
   coming after eighteen others.
2. Constituting or being one of nineteen equal parts into
   which anything is divided.

\Nine"teenth`\, n.
1. The quotient of a unit divided by nineteen; one of
   nineteen equal parts of anything.
2. The next in order after the eighteenth.
3. (Mus.) An interval of two octaves and a fifth.