1. One of forty equal parts.

2. The fourth tenth; being one of forty equal parts.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• forteenth,
• forteh,
• fourteeth,
• fortet,
• fourtieth,
• fortie,
• fortth,
• foreth,
• fortietg,
• fotieth,
• forteth,
• fortiet,
• fortyeth,
• forlaite,
• fortooth,
• Fortilege,
• fortitio,
• fortlett,
• fortiethe,
• forcimets

• fortuitous,
• fourth deck,
• forty-three,
• forthwith,
• fortuity,
• fortitude,
• forty-third.

The adjective form of the word "fortieth" is "fortieth".

The plural of the "fortieth" can be the "fortieths".

The singular of the "fortieth" can be the "fortieth".