Do I Use a Hyphen with Extra?
AP Style holds that you should not use a hyphen with “extra” when it means “outside of” unless the prefix is followed by a word beginning with “a” or a capitalized word. For example, words like the following do not use hyphens,
- Extralegal
- Extramarital
- Extraterrestrial
- Extraterritorial
A hyphen should follow “extra” when it is part of a compound modifier describing a condition beyond the usual size, extent, or degree. For example, words like the following require hyphens,
- Extra-base hit
- Extra-dry drink
- Extra-large order of fries
- Extra-bland flavor