The difference between christmas and christmas day?

A difference in focus:

christmas: includes Christmas eve and Christmas day two days, eve is the night of the 24th, Christmas Eve.

christmas day: christmas day can only be called christmas day.

Second, the difference in usage:

christmas usage:

Used as an exclusive noun, often used in conjunction with about, after, for and other prepositional collocation to form the idiom, and its act as the subject of When it is used as the subject, the context of use is to appear in the article with holiday activities as an opportunity.

Christmas day usage:

As a noun phrase, it is often used in conjunction with Ow, Oh, well, and Psst.

Third, the difference in meaning:

christmas?

Interpretation: n. Christmas activities; turkey day

christmas day

Interpretation: christmas day