* Certain: "I am sure of it."
* Firm: "She held the rope with a sure grip."
However, there are some contexts where "sure" can function as a noun, but it's rare and often informal:
* A sure thing: "The new restaurant is a sure thing for success." (Here, "sure thing" acts as a noun phrase, meaning something guaranteed to be successful.)
* For sure: "I'll be there, for sure." (This is a colloquial expression, with "sure" functioning as a noun adjunct, reinforcing the certainty.)
Overall, it's important to understand the context to determine the part of speech "sure" is functioning as. In most cases, it's an adjective.