To what does the term 'apprehend' most closely relate?

The term 'apprehend' is most closely related to the action of arresting an individual. In legal terminology, to apprehend someone often refers specifically to the act of seizing or taking a person into custody, usually due to suspicion of a crime. While it can also imply a form of understanding when it's used in different contexts, in this instance, the primary and most common usage in law enforcement directly points to the act of arrest.

Understanding a concept, finding a resolution, and completing a task, while they all involve a form of mental processing or accomplishment, do not capture the specific and defined meaning of 'apprehend' as it applies to law enforcement and the context of taking someone into custody.