Transcript:

Hi, I'm Charlie Kasov, and this is, "What is a characteristic of a line?" Now a characteristic of a line is something about the line that makes it distinct from other things in geometry. So a line is actually a one dimensional instance in space and time that has no end points. It goes on infinity this way, goes on to infinity this way. It doesn't change directions ever. A line segment would be the distance between two points, the shortest distance between two points along a line. So a point is an instance in space and time that has zero dimensions, and the distance between these two points, line segment, is one dimensional. Now, even with two lines that go into infinity, if they intersect to form a 90 degree angle, then the two line segments are perpendicular. So, that's another characteristic of a line. A third characteristic of a line is that a line can contain a ray. So here is a line, but if we start from this point and go in this direction, that's a ray. Or if we start from this point and go in the other direction, that's also a ray. So any given line can contain multiple rays as long as it emanates from a point and goes off with no end point.