Originally Posted by historiasdeosos
Why schoolwork but not school work or school-work? Why is well-being the preferred form, not wellbeing or well being? Why help desk but not helpdesk or help-desk?
Having spaces or lacking them depends on whether a given collection of words can have an ambiguous meaning.
Take the musical genre bluegrass, for instance. As separate words, "blue grass" can mean the literal plant grass that is the literal color blue, so you need to stick the two words together to differentiate it. Same with back slash (backwards cut with a weapon, slash someone's or something's back, etc.) vs. backslash (the specific symbol "\"), black bird (a raven or crow) vs. blackbird (a specific species), copy right (correctly reproduce something, the privilege to copy something, etc.) vs. copyright (the specific legal system covering copying privileges and fees), home work (painting your house, working from home, etc.) vs. homework (assignments a student is given to complete outside of school), and so forth.