I have noticed in the list of tag synonyms that a synonym discrete-mathematics $\to$ combinatorics has been suggested. Currently it awaits votes from users.
I am not sure this is a reasonable tag synonym. But I definitely think that such a synonym should not be created without discussing it on meta beforehand - this is a synonym which would influence a very big number of questions.
EDIT: In the meantime, the synonym suggestion has been downvoted to $-2$ and hence removed. (Probably it was noticed partly thanks to this meta post.)