Webster's Revised Unabridged Dictionary · 1913

Nineteenth

Nineteenth , adjective

[Compare Anglo-Saxon nigonteóea.]

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.

Nineteenth , noun

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.
(Music) An interval of two octaves and a fifth.