"Different" is an adjective, and it cannot work alone with "the". "What is the difference between....?" "What are you late?" doesn't exist in English. Perhaps you mean, "Why are you late?" or "What are you late for?" (these are different questions). "You are late" is a fact.

You wouldn't use the first phrase, it does not make sense. The second phrase, "you are late", is correct. It is a statement of a fact.

In English: Why are you " arriving " late? = The "why " it indicates that the person involved requires an explanation to conduct " Tardiness " Why are you late? = Is a less inflexible form of the person who requires explanation , to ask for a justification to conduct " Tardiness " Why are you late ? = It is a more formal and flexible way to politely ask for an explanation. Why did you come so late ? = It is when there is a delay either : a date, a commitment [ ... ] to there and overstepped his arrival. They are variations in the Spanish language. Any of the formerly mentioned- forms are acceptable . :) It is late : It is a statement, a premise that does not lead to explanations. It is a way of saying " You're late ," expressing anger. :) I could teach Spanish . If you want.

"So you would not use "why you are late " as a single sentence right?" - That's right. Although there are two cases when you might here this outside of a full sentence: 1) As an answer two a question. E.g. A: Why are you late? B: Sorry, I didn't catch that. What are you asking about? A: Why you are late. -"Why you are late" isn't a full sentence here. It's short for "I am asking about why you are late". 2) As the title of something like an article or a poster. For example, an online article might be called "Why you are always late". You'd expect the article to be an explanation of why you're always late. In both of these cases (as well as any other time when it's at the end of a sentence), "why you are late" acts like a single noun, and you could replace it with a noun if you wanted e.g. you could say "dogs" as the answer to the question I mentioned before, have it at the title of an article, or say "I am asking about dogs".

You are late. = 你迟到了。 "What are you late"没有意思。可能你的意思是“Why are you late?"。 Why are you late? = 你为什么迟到了？ "...why you are late"（没有问题的词序）也会对， 可是不会是自己的句子。得在句子的后面。 比如： I don't know why you are late. = 我不知道你为什么迟到了。