Candles for a fortieth birthday.
The definition of fortieth is something that occurs after 39 other things have occurred, or that occurs in the position identified by the number 40.
The birthday after your 39th birthday is an example of your fortieth birthday.
- preceded by thirty-nine others in a series; 40th
- designating any of the forty equal parts of something
Origin of fortiethMiddle English fourtithe from Old English feowertigotha: see forty and -th
- the one following the thirty-ninth
- any of the forty equal parts of something;
in the fortieth place, rank, group, etc.
- The ordinal number matching the number 40 in a series.
- One of 40 equal parts.
- The ordinal form of the number forty.
- The person or thing in the fortieth position.
- One of forty equal parts of a whole.