1. Also known as parabolic rule.

2. A basic approximation formula for definite integrals which states that the integral of a real-valued function f on an interval [a,b] is approximated by h[f (a ) + 4f (g + h ) + f (b )]/3, where h = (b - a )/2; this is the area under a parabola which coincides with the graph of f at the abscissas a, a + h, and b.

3. A method of approximating a definite integral over an interval which is equivalent to dividing the interval into equal subintervals and applying the formula in the first definition to each subinterval.

A mathematical relationship for calculating the oil- or gas-bearing net-pay volume of a reservoir; uses the contour lines from a subsurface geological map of the reservoir, including gas-oil and gas-water contacts.