Sure vs Surely? What’s the difference?

The difference between “sure” and “surely” is that “sure” is an adjective and “surely” is an adverb. While both refer to a kind of solid certainty, they serve disparate grammatical roles. The best way to remember this is the –ly at the end of the word; it’s almost always an indicator of an adverb.

While this can get confusing, it doesn’t have to be. The difference in spelling is the key to recognizing the difference and utilizing them properly. As a tip, whenever you see –ly at the end of any word, it’s more than likely an adverb.

Definition; Use of “Surely”

“Surely” is an adverb to express a sense of definitiveness or certainty. It can also be a comment of surprise or amazement. Whenever you use “surely” at the beginning of a sentence, a comma (,) follows behind it.

  • Certainty: They surely can’t believe the lies that come out of broadcast news.
  • Amazement: Surely, you don’t expect me to trust anything they say on broadcast news!
  • Certainty: Surely, they won’t get further than five feet until they realize their laces are missing.
  • Amazement: Surely, they didn’t realize their laces were missing.
  • Certainty: You will surely ruin Thanksgiving just by burning the turkey.
  • Amazement: Surely, you can’t ruin Thanksgiving just by burning the turkey.

Definition; Use of “Sure”

“Sure” is a perfect adjective to describe something or someone as being certain or definitive about any given topic. However, “sure” can also be an adverb on rare occasions.

  • Adjective:  I was sure I put the keys on the mantle.
  • Adjective: The football team is sure about winning the next game.
  • Adjective: The only sure things in life are death and taxes.
  • Adjective: The ballerina moves about gracefully amid a sure flow of rhythm.
  • Adverb: He sure was angry after running his head straight into a brick wall.

“Sure” has also become a way to respond to a suggestion or thank you.

Mnemonic Device

To remember the difference between “sure” and “surely” is the indication of the –ly at the end. When in doubt, use “certain” or “certainly” as a synonym to see if it works. Also, try to remember the following phrase:

Surely, we can be sure about adverbs versus adjectives.


Understanding the difference between “surely” and “sure” can be a little tricky. But, if you can remember the –ly at the end of “sure” makes it an adverb, it will be as easy as pie.