an opaque, spherical, and solid body like a planet, performing revolutions about the sun in elliptical orbits, which have the sun in one of their foci.

There is a popular division of comets into tailed, bearded, and hairy comets; though this division rather relates to the different circumstances of the same comet, than to the phenomena of several. Thus when the light is westward of the sun, and jets after it, the comet is said to be tailed, because the train follows it in the manner of a tail: when the comet is eastward of the sun, and moves from it, the comet is said to be bearded, because the light marches before it in the manner of a beard. Lastly, when the comet and the sun are diametrically opposite (the earth between them), the train is hid behind the body of the comet, except a little that appears round it in form of a border of hair: and from this last appearance the word comet is derived; as κομήτης, cometa, comes from κόμη, coma, hair. But there have been comets whose disk was as clear, as round, and as well defined, as that of Jupiter, without either tail, beard, or coma. See Astronomy Index.