Sometimes, it’s not spelling that makes all the difference. It’s choosing whether or not to write something as one word or two. That extra space (or its absence) is important, just like how a simple hyphen can transform “recreation” (an activity you do for fun) to “re-creation” (the act of creating something again). So, what’s the difference between writing “someday” as one word and “some day” as two?

The Indefinite Someday

When written as a single word, someday is an adverb that refers to something that will happen at some indeterminate and indefinite time in the future. It’s some unspecified future time.

  • I’m going to be a successful YouTube celebrity someday.
  • Someday, I’ll get around to visiting Easter Island.
  • Baggy jeans will be fashionable again someday, right?

The Unspecified Some Day

The most important difference to remember with some day written as two words is that “some” function as an adjective modifying the noun “day.” In this way, “some day” refers to a very specific, single day, even if the exact day itself is unknown or unspecified.

  • Stephen Hawking was born some day in 1942.
  • My friend is coming to visit me some day next month.
  • You’ll receive the test results some day in the next week or two.

While traditionalists have made a clear distinction between the two terms, Oxford Dictionaries recognizes the rising tendency to “fuse fixed expressions,” more so in American English than in British English. As a result, occurrences of “someday” outnumber “some day” in American English by a factor of about 4-to-1. Even when someone might really mean “some day,” they could just write “someday.”

Some Day or Someday Pop Quiz!

Just as how the difference between “every day” and “everyday” can seem confusing at first, differentiating between “someday” and “some day” may require a little bit of practice. So, here’s a little bit of practice.

  1. Your tax return is due (some day / someday) next month.
  2. We hope that (someday / some day), none of this will matter.
  3. Is this going to get cheaper (some day / someday) or not?
  4. (Some day / Someday) you’ll look back and remember what you did.
  5. I really ought to redeem this offer (someday / some day).

Comment with your answers below!