Someday vs. Some Day – What’s the Difference?

The meanings of some words and phrases are so similar that it’s difficult to see an appreciable difference. Why, for instance, does English have words like stairway and staircase, which appear to have no appreciable difference in meaning?

Likewise, the difference between someday and some day seems unclear at first blush. Why does the space matter?

Although someday and some day are indistinguishable in spoken English, they are actually different parts of speech. Precise writing depends on using words intentionally, so you will want to know when each of these terms is appropriate.

What is the Difference Between Someday and Some Day?

In this article, I will compare someday vs. some day. I will use each of these words in at least one example sentence, so you can see them in context. Plus, I will give you a useful mnemonic that will help you choose someday or some day for your own writing.

When to Use Someday

someday versus some day What does someday mean? Someday is an adverb and is defined as at an undetermined time in the future. It describes when an action or event will take place.

Here are some examples,

  • Someday, let’s climb to the top of the water tower with bottle rockets and shoot them down into the river.
  • I will be mayor someday, and you crooks will have a lot to answer for when that time comes.
  • Someday, a great rain will come and wash all the garbage from the face of the earth.
  • It bought the 101 remaining lots in the neighborhood for a total of $375,000 and spent about $550,000 finishing half-built lots and upgrading the pool and clubhouse, betting home builders someday would return to the area. –The Wall Street Journal

Someday, spelled as a single word, refers to sometime in the indefinite future. It is unspecific and does not necessarily imply an actual 24-hour day.

For instance,

  • Someday, I will become famous.

This isn’t referring to an actual day; it’s simply referring to an undetermined time in the future. In this case, the one word someday is used.

When to Use Some Day

Definition of some day definition and definition of someday definition What does some day mean? Some day is a phrase that refers to a 24-hour span of time in the future that has not yet been specified.

In this sense, day is a noun, and some is an adjective that means not yet determined.

The following sentences are examples,

  • Some day next week, we need to finish these audits so corporate stops breathing down our necks.
  • Let’s find some day when we’re both free and grab a coffee at that café down on 50th and Division.

The noun could just as easily be plural, like in these two examples,

  • Some days are rainy, but some days the sun shines over a glittering coastline as far as the eye can see.
  • At a normal office, you take breaks — grab a cup of coffee with co-workers, take the occasional walk, maybe even eat away from your desk some days, to break up the day. –The Washington Post

The important takeaway from these examples is that some day, spelled as two words, uses the word day to refer to a discrete unit of time. When day retains its noun sense and refers to a discrete 24-hour period, the two-word some day is used.

  • Let’s get lunch some day next week.

In this example, you are referring to days in the upcoming week, not just an unspecific time in the future.

Trick to Remember the Difference

Define some day and define someday Here is helpful trick to remember some day vs. someday

  • Someday is an adverb.
  • Some day comprises an adjective and a noun.

It can be difficult to remember when to use each of these terms. However, by remembering that the word day is a noun, you can also remember that some day is a noun phrase, rather than an adverb.


Is it someday or some day? Someday and some day are two English terms that many writers misuse.

  • Someday is an adverb that situates an action or event at a vague point in the future.
  • Some day is a noun phrase that refers, similarly, to a unspecified 24-hour period, also at some point in the future.

Since the word day by itself is a noun, you can easily remember that some day is a noun phrase, not an adverb.

In summary, the compound word someday is an adverb. The two-word phrase some day comprises an adjective and a noun.