They are two totally different art movements, and I love do my best to explain them to you in a few paragraphs. Let's start with expressionism: It originated around the beginning of the 20th century, a precursor being Edvard Munch. read more
In simple words works done in surrealism has the dream like quality, and fine works are done in this time period, focusing a lot to the details and emphasize is also given on perspective, Salvador Dali is the man to remember every time you mention about Surrealism. read more
The difference between expressionism and surrealism isn't something, to my knowledge, that has been precisely quantified; a skilled argument could interpret a work generally considered expressionist as surrealist if it focused on the right criteria. read more