Semi Latus Rectum of Ellipse is half of the line segment passing through any of the foci and perpendicular to the major axis whose ends are on the Ellipse. And is denoted by l. Semi Latus Rectum of Ellipse is usually measured using the Meter for Length. Note that the value of Semi Latus Rectum of Ellipse is always positive. Typically, the value of Semi Latus Rectum of Ellipse is greater than 0.