The SVG <line> element defines a straight line. A line has starting coordinates and ending coordinates. In addition, a line can have stroke, stroke-width, and stroke-opacity properties.
Thus, you can completely define a line in SVG like this, which defines a line running diagonally from the upper-left corner of an SVG image toward the lower-right corner. I have also included a second line whose stroke-opacity property is 0.5 as shown in Figure 03.04. (The line is semitransparent, so you can see how that setting affects the rendering of the line.)