What does fortieth mean?
"Fortieth" is the ordinal form of the number forty, denoting the position that comes immediately after the thirty-ninth in any ordered sequence — as in the fortieth floor, the fortieth chapter, or the fortieth year. Used chiefly as an adjective, it frequently marks milestones: a fortieth birthday, a fortieth wedding anniversary (traditionally the ruby anniversary), or a fortieth edition of a work. Less commonly, it functions as a noun meaning one of forty equal parts of a whole, equivalent to the fraction 1/40. In abbreviated form it is written 40th. Like "forty" itself, the word drops the "u" present in "four," a quirk of English spelling that has confused writers for centuries. Geographers even speak of the fortieth parallel, a line of latitude crossing much of the United States, Europe, and Asia. Whether counting years, pages, or degrees, "fortieth" provides the precise, conventional way to express this position in a sequence.
Coming next after the thirty-ninth in order; being number forty in a sequence.
"He lives on the fortieth floor of the tower."
Abbreviated numerically as 40th.
One of forty equal parts of a whole; the fraction 1/40.
"Each shareholder received a fortieth of the estate."
Pluralized as "fortieths" when referring to multiple such parts.
Used only in the noun sense, when describing multiple units each equal to one part in forty.
"The recipe measured ingredients in fortieths of a barrel."
A couple's fortieth wedding anniversary is called their ruby anniversary — forty years of marriage earns the gemstone.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of fortieth
"Fortieth" derives from the Old English "fēowertigotha," combining "fēowertig" (forty) with the ordinal suffix "-oth." The root "fēowertig" itself comes from "fēower" (four) plus "-tig," a suffix meaning a group of ten, so forty literally means "four tens." This Germanic lineage makes the word a cousin of related English terms built on the same root, including "four," "fourteen," and "fortnight" (originally "fourteen nights"). The shortened spelling without the "u" of "four" was established in "forty" and carries through to "fortieth."
Related word forms
How fortieth is actually used
As an ordinal, "fortieth" is written 40th. Note the spelling: like "forty," it drops the "u" found in "four." It is neutral in register, used equally in formal and informal contexts, most often for birthdays, anniversaries, and enumerations such as floors, chapters, and editions.
Easily confused with fortieth
"Forty" is the cardinal number 40 indicating quantity, while "fortieth" is the ordinal indicating position number forty in a sequence.
"Fourteenth" relates to the number fourteen in a sequence, whereas "fortieth" relates to forty — they sound somewhat similar but denote very different positions.