sure is....
I've heard a dialog and it's gone like this:
A: Good party, isn't it?
B: Sure is.

Is ( sure is ) well-formed?
what does it mean?
Formal or informal?

Thanks.

Question

sure is....
I've heard a dialog and it's gone like this:
A: Good party, isn't it?
B: Sure is.

Is ( sure is ) well-formed?
what does it mean?
Formal or informal?

Thanks.

Answer

Sure is means the part is surely a good party. This is a common expression used that means"yes" to any question. sure are sure am also.

Answer

"Sure is!" is a shortened form of "It sure is (a good party)!"  (It certainly is a good party!)

It is very common to answer a question like this in this way. It is quite informal.