as infinite or indefinite ellipses, defined by the indefinite equation $ay^m + bx^n = c$, when $m$ or $n$ are greater than 1; for when they are each = 1, it denotes the common ellipse.

There are several kinds or degrees of ellipsoïdes, denominated from the exponent $m + n$ of the ordinate $y$. As the cubical ellipsoïde, expressed by $ay^3 = bx^2 - x$; the biquadratic, or fusifoloid $ay^4 = bx^3 - x^2$; &c.