Abscess, or Abscessa, is a part cut off from a straight line, and terminated at some certain point by an ordinate to a curve; as AP (fig. 2.), or Plate II. BP (fig. 3.). The abscess may commence either at the vertex of the curve, or at any other fixed point; and it may be taken either upon the axis or upon the diameter. Absorption, meter of the curve, or upon any other line drawn in a given position. Hence there are on the same given line or diameter an infinite number of variable abscissas, terminated all at one end by the same fixed point. In the common parabola (fig. 4.), each ordinate $PQ$ has but one abscissa $AP$. In the ellipse or circle (fig. 2.), the ordinate has two abscissas lying on the opposite sides of it. In general, to each ordinate a line of the second kind, or a curve of the first kind, may have two abscissas; a line of the third order, three; a line of the fourth order, four; and so on.