Compound words can be tricky. A compound word is a combination of two or more words that function as a single unit of meaning. Some compound words stand as two separate words or open compounds. Others consist of two words bumped together, closed compounds, and still others are hyphenated compounds.
You would think there has to be some rule as to when a compound is open, closed, or hyphenated, right? Not really, or at least I’ve never been able to find one.
Most compounds start out as two separate words. Then as the term becomes more popular, the words are hyphenated, and if they end up being really popular, they are bumped together, creating a closed compound. My suggestion for always using the correct treatment for compound words? Look them up, each time, every time, even if you think you know how it should be. MS Word helps somewhat with compounds, but it’s not foolproof. Look it up.
If you want to see how good you are with compound words, take this quiz of seventy-five compounds designed by DailyWritingTips.com. I got a good many of them correct, but not enough to forego looking them up in the dictionary. Let me know how you do.