A few years ago, a student journalist wrote a profile for a class that recalled how she found her calling:
“Her love for photojournalism came from spending evenings in a dark room with her father.”
The student could not understand why the professor doubled over with laughter.
“I think you meant darkroom, not dark room,” the prof said.
“What’s the difference?” asked the student, who knew only of digital cameras.
“One is a room for developing film and printing photos,” the prof said. “And the other is a room without much light. You’ve written that she spent many evenings with her father in a room without much light, which implies something other than film may have been developing.”
“Whatever,” the student shrugged.
In English, the application of many words can vary depending on whether they are rendered as one word or two. We’ve already discussed pairs like “every day/everyday” and “anytime/any time,” but those are just variations on a theme, the same definitions applied in different situations.
Other words, like “darkroom/dark room,” actually change meaning through that simple space.
Not all such pairs will have the same effect as the student’s mistake did. But using the wrong version can impede meaning. “She’s waiting for you in the green house” and “She’s waiting for you in the greenhouse” poses a choice as to where to go to meet her. A sentence discussing a library would have a very different impact depending on whether it mentioned “the plethora of bookworms” or “the plethora of book worms” there. A question about whether the restaurant has “hotcakes” could yield a very different dish if it asked about “hot cakes.”
Spoken English can provide clues as to which one is meant through the emphasis on one syllable over another. A book buyer puzzled at being handed a tome on angry expressions might realize he asked for a “cross WORD book” instead of a “CROSSword book.” But that option is not available in written language, though “hearing” the word you want can help guide you.
Sometimes the differences between versions are minor: Is there a difference between a “pass word” and a “password”? Between “backup” and “back up,” aside from one being a noun, adverb, or adjective and the other usually being a verb?
So many of our words started as two and became one—we’re seeing that with “web site,” which is fast becoming “website” universally—that one might think it doesn’t matter. But nuance sometimes requires the sundering of that which had cleaved as one word. “I cannot go there” does not mean the same thing as “I can not go there.” One means “I am unable to go there,” while the other is “I am able to avoid going there.”
Over all, let your ear be your overall guide. Oh, and that word in the subheading, “spaceage”? We made it up (though Urban Dictionary has a definition). Bet you understood it, though.