How should you spell the number 40? It seems obvious because the number four is spelled with a “u,” so therefore it’s spelled fourty right? Unfortunately, it's not that simple. The correct spelling is forty, but why?
Why Isn't There a U in "Forty"?
There is understandable confusion about the inconsistency between the spelling of the numbers that contain the number four. For example:
But why is the “u” standard for the spelling of four and fourteen but not forty? Well, it all comes down to its origin.
The Origin of "Forty"
The word forty can be traced back to an Old English compound word feowertig that combines feower (four) and tig (group of ten). So, the spelling of forty without a “u” has been popular since at least the16th century. Even the Bard himself, William Shakespeare, spelled it without a “u.”
Although the spelling of forty is and has been fixed for centuries, the variant spelling fourty makes its way into articles and literature from time to time. However, this use of fourty does not make it correct. Forty is always the correct spelling.
When to Write "Forty" vs. "40"
Forty is used in a variety of ways to indicate the number 40 or forty-something. It can be expressed in written or numerical form.
The restaurant could fit about forty people.
The speed limit was forty miles per hour.
I am forty-one years old.
It is notable that numbers above 10 are typically written in numerical form in AP style. Some other writing style guides recommend writing "forty," and there are always exceptions to rules. You can always familiarize yourself with all of the standards for when to spell out numbers.
How to Remember the Correct Spelling
While it is difficult to remember the spelling of forty and other such words, the best solution is to simply study and memorize the correct spelling. This includes other commonly misspelled words with only one correct spelling like lense and lens.
There are also words where there is one agreed-upon correct spelling, but an alternative spelling is correct and widely used too such as thru and through. Whenever you come upon a word you are not sure about, use your judgment and consult your trusted dictionary for the correct spelling to be sure.