When two or more words team up to describe something, they’re usually hyphenated to make their symbiotic relationship clear. Each of the following sentences contains a phrasal adjective that should be linked with one or more hyphens; each example is followed by a brief discussion and a revision.
1. Their affair wasn’t exactly the best kept secret.
This sentence refers to a secret that is the best kept, not a kept secret that is better than any other, so link the phrasal adjective together: “Their affair wasn’t exactly the best-kept secret.”
2. The company conducted an information security risk assessment earlier this year.
What type of assessment occurred? A risk assessment about information security, or an assessment about information-security risk? Either analysis is correct, but at least one hyphen is required, no matter which interpretation is favored: “The company conducted an information-security risk assessment earlier this year” and “The company conducted an information-security-risk assessment earlier this year.” (Both work, but the former alternative is simpler.)
3. Smith is widely revered for being the most high profile member of the Mormon faith in America.
This sentence seems to imply that of all the profile members of the Mormon church, Smith is the one most intoxicated by drugs. A hyphen linking high and profile eliminates any confusion about the meaning of the statement: “Smith is widely revered for being the most high-profile member of the Mormon faith in America.”
4. The rare book dealer has been in business for as long as I can remember.
Does this sentence refer to one of the few book dealers or to a dealer in rare books? The latter reading is more likely, but eliminate doubt by hyphenating rare and book: “The rare-book dealer has been in business for as long as I can remember.”
5. We analyzed the entire play on a scene by scene basis.
The phrasal adjective “scene by scene” should be hyphenated: “We analyzed the entire play on a scene-by-scene basis.” (Alternatively, simplify the sentence to “We analyzed the entire play scene by scene”; try this approach for time frames, too, as by replacing “on an annual basis” with annually.)