What happened to the “u” in forty?

22 Jun What happened to the “u” in forty?

Here’s another question I was asked recently: What happened to the <u> in forty?  I have two answers: The long one and the short one.

Here’s the long answer:

First, I have to first explain a couple cool things about the English language.

1.  In English, whenever possible, words that sound the same but have different meanings are spelled differently.  Some might argue this is problematic, but it’s really quite a perk.  Consider this sentence: The _______ carrier brought us a package.  If we spelled words with different meanings the same way, you’d have no way of knowing whether I intended to say the carrier was a man or whether I was further defining the job of “carrier” as “bringer of the mail”.    The purpose of text is to get meaning to our reader as quickly as possible, and having different spellings for words assists in that goal.
2. All our English words can be grouped into two broad categories: function words and content words.  Content words are the words that convey meaning, the nouns, verbs, adjectives, and adverbs.  We add new words to this category all the time (think “selfie, photobomb, hangry”).   Function words are the words that glue the content words together, such as determiners, prepositions, pronouns, conjunctions, etc.
   Function words tend to be as short as possible, so if you have a function word and a content word that sound the same, the function word will be shorter.  Think about <by> and <bye>.  Also, content words were felt to need more visual weight, so they typically have three or more letters (e.g., <inn, egg, ebb>).

Now let’s talk about <four> and <fourth> while thinking about the first principle above.  Because we also have the words <for> and <forth>, different spellings were used for the numbers to reduce processing time for readers.  And because <for> is a function word, it took the shorter spelling.  But this still leaves us wondering about the <u> in <forty>, right?  Numbers can be considered to be somewhere on a spectrum between function words and content words, so as their spellings evolved over time, they tended to move towards being as small as possible.  Because there was no homophone constraint on the spelling <forty>, over time, that’s how English spellers began to spell it.

And here’s the short answer: Why no <u> in <forty>?  Because that’s how it evolved.

A fancy graphic I created for you to explain the spelling of ‘forty’ .