Quote Originally Posted by David Goldstein View Post
As I recall from my police days, it was legally classified as an arrest. A police officer is not required, (in the U.S., anyway), to inform people they are talking to in an official capacity that they are under arrest. Police officers can also allow people to go on their way once they are satisfied.

Keep in mind, I am talking about when an officer is officially conducting police business, such as an investigation.
Yes, you're right. The word arrest can be applied to detainment, that is, a person can be arrested and detained.
But there's a distinction between that and the more commonly used and understood meaning of the word, and even more so with the term "under arrest", which was used in the post to which I replied.