What is the ruling on phrases such as "upside down" and "right side up?" Do they receieve any hyphens at all?
I'm getting contradictory rulings from multiple sources.
For example,
http://www.merriam-webster.com/dictionary/upside%20down says that "upside down" only receives a hyphen when it's used as an adjective. If used as an adverb, however, it stays as is.
Other sources either say the exact opposite or that they never get hyphens. Which one is it?
Here's a sentence with "right side up" in it:
"Place the letter 'e' on a clean microscope slide right side up." Hyphen or no?