|Definition - A phrase regarded as a noun.|
Example - There are three types:
(1) open compounds: these are spelled as separate words
(e.g. bed rest)
(2) hyphenated compounds: these are joined by hyphens
(3) solid compounds: these are spelled as one word
Note: There is an additional distinction made between
(1) permanent compounds: Those that are dictionary entries, and
(2) temporary compounds: Those that are formed for an ephemeral purpose.
1. When showing possession, always put the possessive apostrophe at the end of the compound noun.
mother-in-law's horse (good)
mother's-in-law horse (bad)
2. Don't hyphenate the words when hyphenation is not needed to clarify the sense.
3. Retain the original compound's form (e.g. solid or hyphenated) in expressions that are derived from it.
"footnoting" from "footnote"
4. Use hyphens to avoid double vowels or triple consonants.
de-emphasize and mall-like