Does a circle have area, and does the cube have a volume?

Question

A circle is just the line which is apart from the centre by a constant value so does a line have area?

And my second question is does a cube occupy a volume?

Answer 1

You need to distinguish between the perimeter of the circle, which is a curve without area (one can also consider it to have area $0$), and the disc enclosed by the circle, which has area $\pi r^2$.

In everyday language, the word "circle" is used for both of these concepts, and one can usually guess from context which of them is meant.

In careful mathematical language, "circle" usually tends to mean only the perimeter curve, and the disc is called a disc, but there are some traditional exceptions where even mathematicians say "circle" about the disc. In particular, speaking about the area of geometrical figures ("area of the circle", "squaring the circle", etc) is such a common exception.

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For cubes not even mathematics has a well-established convention that provides different words for the solid and its surface. Both are called "cube", and it is up to the speaker to provide enough context to make it clear whether he means the polyhedral surface or also its interior.