An open curve all points of which are equidistant from a fixed point, called the FOCUS, and a straight line. The limiting case occurs when the point is on the line, in which case the parabola becomes a straight line.
Related Terms 
POINT OF TANGENCY
The point at which a road curve or railway curve becomes straight or changes its curvature. Also known as tangent point.

POINT OF INTERSECTION
The point at which two straight sections or tangents to a road curve or rail curve meet when extended.

PERFORMANCE CHART
Graphical representations showing the abilities of rotating equipment at various operating conditions; for example, the performance curve for a compressor would include rotor speed for various intake and outlet pressures versus gas flow rate adjusted for temperature, density, viscosity, head, and other factors.

MASSHAUL CURVE
A curve showing the quantity of excavation in a cutting which is availableforfill.

INVOLUTE GEAR TOOTH
A gear tooth whose profile is established by an involute curve outward from the base circle.

EMISSION SPECTROMETER
Works on the basis that atoms of metallic and other particular elements emit light at characteristic wavelengths when they are excited in a flame, arc, or spark. Excited light is directed through an entrance slit in the spectrometer. This light penetrates the slit, falls on a grate, and is dispersed and reflected. The spectrometer is calibrated by a series of standard samples containing known amounts of the elements of interest. By exciting these standard samples, an analytical curve can be established which gives the relationship between the light intensity and its concentration in the fluid.

HYPERBOLA
An open curve with two parts, all points of which have a constant difference in distance from two fixed points called FOCI.

CUTWATER
The forward curve of the stem of a ship

ASYMPTOTE
A straight line or curve which a curve of infinite length approaches but never quite reaches

CATENARY
The curve formed by a uniform cable supported only at its ends. Navigators are concerned with the catenary of overhead cables which determines clearance underneath, and the catenary of the anchor rode, which in part determines holding power and swing circle.
