For"ti*eth (?), a. [AS. feowertigoa. See Forty.]
1.
Following the thirty-ninth, or preceded by thirty-nine units, things, or parts.
2.
Constituting one of forty equal parts into which anything is divided.
© Webster 1913.
For"ti*eth, n.
One of forty equal parts into which one whole is divided; the quotient of a unit divided by forty; one next in order after the thirty-ninth.
© Webster 1913.