In "Medical team", Medical is an adjective. In "Legal team", legal is similar. But in some situations, some people use only "Medical" or "Legal" , eg "Get approval from Legal team" becomes "Get approval from Legal". What is this usage called ? How old is this type of usage ?
There are cases where this usage does not work, eg "Secret service" cannot be shortened to "Secret". What are the general "rules" of where this shortening works and where it does not ?