I see a lot of Halachic and Aggadic texts where the words גוי, נכרי, עכו"ם are all used interchangeably. Usually I notice it in places where two people are using different versions of a text (one from a newer publication, one an older version), and one version has one word, and the other version the other word. Is one of these words considered more politically correct than the other? More modern? Less modern? What's the deal with the substitutions?