When is artwork one word and when is it two?

The term "artwork" is one Word when referring to a piece of art, such as a painting or sculpture, treated as a single entity. It is two Words, "art work," when used to describe the process of creating art or when discussing art as a general category, such as in phrases like "the art work of the students." Context determines the usage, so it's essential to consider how the phrase is being applied.