Feature on a gnomon that allows viewers to see the shadow of a single point, as opposed to that of a post or edge. A nodus often enables the dial tell the date as well as the time.

a point which casts a shadow to indicate the time and/or (more often) the date on a dial face. It may take the form of a small sphere or a notch on a polar-pointing gnomon, or it may be the tip of a gnomon with an arbitrary (usually horizontal or vertical) orientation.

indention or notch along front margin of wing, generally centrally located.