"He is a vegetarian."
Translation:Anh ấy là người ăn chay.
You can say that in conversation and a human would understand what you mean but only certain answers have been loaded into the DL computerised answer list. "Người không ăn thịt" literally translates to "Person not eat meat." While that may infer someone is a vegetarian it does not strictly translate to He is a vegetarian. The Vietnamese word for "he" is anh ấy and the Vietnamese words/phrase (and there are others) for the English noun "vegetarian" is "người ăn chay." Therefore "He is a vegetarian" is "Anh ấy là người ăn chay."