This will draw an ellipse

cx is the x co-ordinate of the center of the ellipse, cy is the y co-ordinate at the centre of the llipse. rx is the horizontal radius and ry is the vertical radius. Play about with these settings and see what happens. 

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20000303 Stylable//EN"
"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="400" height="400">
<ellipse cx="200" cy="200" rx="100" ry="50"
style="fill:rgb(255,0,0);
stroke:rgb(0,0,255);stroke-width:2"/>
</svg>

view this example here