Annular refers to something that is shaped like a ring or a hardware washer). The term is used in different contexts, including mathematics, astronomy, and medicine. Here are some examples:

• Mathematics: In mathematics, an annulus is the region between two concentric circles). The area of an annulus is the difference in the areas of the larger circle of radius R and the smaller one of radius r). The adjectival form is annular (as in annular eclipse) ).

• Astronomy: In astronomy, an annular solar eclipse happens when the Moon passes between the Sun and Earth, but when it is at or near its farthest point from Earth. Because the Moon is farther away from Earth, it appears smaller than the Sun and does not completely cover the Sun. As a result, the Moon appears as a dark disk on top of a larger, bright disk, creating what looks like a ring around the Moon. Annular eclipses are the rarest kind of solar eclipse.

• Medicine: In medicine, annular refers to a skin lesion that is ring-shaped. An annular lesion is usually red and scaly on the edges and may be itchy or painful.

In summary, annular refers to something that is ring-shaped or has the shape of a washer. The term is used in different fields, including mathematics, astronomy, and medicine.