A playful American respelling of socks. It is not a different word and not a different meaning — same thing on your feet — just a shorter, snappier spelling that advertisers liked because it looks bold and fits on a label or a sign. You will see it on packets in shops, in shop signs, and in brand names. Its most famous use is in baseball: the Boston Red Sox and the Chicago White Sox, two of the oldest teams in American baseball, both spell their name this way, and for many people that is the only place they ever meet the word. Because of that, "Sox" alone in an American sports conversation usually means one of those teams rather than clothing. Do not use this spelling in schoolwork, exams or any serious writing — it will simply look like a mistake. Write socks.