I often see press releases from non-profits or NGOs talking about "at-risk" youth or groups that are most "at risk" of one horrible thing or another. The thing is, none of them seem consistent as to whether or not the hyphen is supposed to be used, or if it's supposed to be used in one situation, but not another.
I looked up the definition of at-risk (with hyphen), and this is what Oxford Dictionaries Online says:
Adjective Vulnerable, especially to abuse or delinquency:
'a church-run school for the most at-risk children'
Then I looked up at risk (no hyphen) in ODO and this is what it said:
Exposed to harm or danger:
'23 million people in Africa are at risk from starvation'
It looks to me like at-risk is used when immediately preceding the noun that it is describing, like in "at-risk children", while at risk is used when you are using a preposition, like "at risk from starvation" or "at risk of memory loss."
If this is the case, is there any source or style guide that prescribes or explains this phenomenon? After some internet searching, I wasn't able to find anything that documents the usage of hyphens to turn phrases into adjectives.
Best Answer
At risk is a prepositional phrase, in which risk is a figurative location. You are at risk when you are in a continual state of risking some sort of harm. (English likes to conceptualize abstract states as locations, each with its obligatory preposition: in danger, in love, on cloud nine, under the weather, ... please suggest more examples in the comments.)
Adding a hyphen, at-risk, transforms the phrase into an adjective, meaning "the modified noun has the property of being at risk". You can use hyphens this way with any prepositional phrase. For instance, suppose you have
you can turn that into
with basically the same meaning. However, it is unusual to do this with "ordinary" prepositional phrases. At-risk gets used this way a lot because it's neutral -- it expresses no judgment on how the group at risk got to be that way. That's important when you're an NGO trying to help people. So it is preferred to more colorful terms (e.g. impoverished) which, in English, often carry a weight of moral disapproval.