I encountered the following claim on a website:
Geometrically, a plane is just a linear object in more than two dimensions. A line is, of course, a linear object in two dimensions. And linear means that it has constant slope (in each direction).
This makes no sense to me. A plane is clearly a two-dimensional object, and a line is a one-dimensional object. But this excerpt says that a plane is a linear object in more than two dimensions, and a line is a linear object in two dimensions? What does this mean and how is it different from my understanding?
I would greatly appreciate it if people could please take the time to clarify this and elaborate.