What is a meant by cross section?

Answer 1

Imagine that you wanted to cut a globe or a sphere exactly in half. When you looked at the cut you would see an exact circle on both pieces. This area would be the cross-section. You could work out the area of this cross-section by using A = Pi X r squared. But be careful. Don't assume that the cross sectional area is the same no matter where you cut. If you cut the globe at some other point, say near to the edge, the cross-section (the circular area that you would see) would be a lot smaller. You would come across a uniform cross-section if you cut a cable. No matter where you cut the cable the cross-section should be roughly the same.

Also cross section doesn't have to be circular. The cross-section you get really depends on the original shape you are dealing with. If you cut a cube in half, you would get a square cross-section.

So I guess you could imagine the term as applying to cutting across (hence cross) something to reveal 2 sections (hence section).