hyphen in compound modifiers
When two words before a noun take a hyphen.
Hyphenate a compound modifier before a noun: a well-known rule, a high-risk plan. No hyphen when the compound follows the noun: the rule is well known. Do not hyphenate after an adverb ending in -ly. See also hyphen with adverbs ending in -ly.
Examples
Usea well-known rule
UseThe rule is well known.
Avoida well known rule