You can tell a text is written in third-person if the author or narrator uses pronouns such as "he", "she", "they", "them" etc. to describe the characters. These pronouns are used when the subject is being spoken about. Now, third-person limited follows the same rules but it limits the point of view of the narrator. In third-person limited, the narrator can only know the thoughts and feelings of one character in the story. A good example of this can be found in the Harry Potter books, where the narrator refers to Harry Potter by his name or by "he", and where the narrator knows Harry's throughts and feelings, but doesn't know the thoughts or feelings of anyone else. "As Harry squelched along the deserted corridor he came across somebody who looked just as preoccupied as he was..."
That's how you know if a passage is written in third-person limited
