What does this mean or what this is mean?

Question

I'm learning English and generally used "what this is mean", but I see many using "what does this mean". Is the way I speak incorrect or informal?

Answer 1

Questions like the one you are asking about are constructed with a form of "to do" as an auxilliary verb, not with a form of "to be".

Let's look at a declarative sentence first:

The cat eats.

To make this into a question that can be answered with yes or no, you use a form of "to do" as an auxilliary verb:

Does the cat eat?

To make the declarative sentence into a question for further information, you also use a form of "to do" as an auxilliary verb:

What does the cat eat?

So, in your case, the declarative sentence could be:

This means that the cat is hungry.

and the question form would be

What does this mean?

If you change the tense from simple present to present progressive, you already have a form of "to be" as an auxilliary verb in the declarative sentence:

The cat is eating.

In this case, you can just use the form of "to be" to build a question, you don't need a form of "to do" as an additional auxilliary verb. So the question would be

Is the cat eating?

But the sentence you asked about isn't in present progressive, it is in simple present. Because of that, you need a form of "to do" to build a question.