ellipse

noun

el·​lipse i-ˈlips 

e-

1

a

: oval

b

: a closed plane curve generated by a point moving in such a way that the sums of its distances from two fixed points is a constant : a plane section of a right circular cone that is a closed curve

2

: ellipsis

Illustration of ellipse

• F F' foci
• P P' P'' any point on the curve
• FP + PF' = FP'' + P''F' = FP' + P'F'

Did you know?

The Property of an Ellipse

A closed curve consisting of points whose distances from each of two fixed points (foci) all add up to the same value is an ellipse. The midpoint between the foci is the center. One property of an ellipse is that the reflection off its boundary of a line from one focus will pass through the other. As a result, in an elliptical room, a person whispering at one focus is easily heard by someone at the other. An oval may or may not fit the definition of an ellipse.

Examples of ellipse in a Sentence

Recent Examples on the Web

The Oakley Ellipse 50th Anniversary pair, designed to reflect the ellipse of the Oakley logo, retains the brand's futurist aesthetic with the lens shape and curve, known at Oakley as the PhysioMorphic Geometry. —Cassell Ferere, Forbes.com, 14 July 2025

That orbit in general is an ellipse, an oval shape. —Phil Plait, Scientific American, 25 July 2025

The ellipse enclosing these locations is called an error ellipse. —Toshi Hirabayashi, Space.com, 23 July 2025

Trajectories are calculated to within meters per second, and landings must fall inside an ellipse of just a few meters after traveling millions of kilometers. —Shekar Natarajan, Forbes.com, 27 June 2025

Word History

Etymology

Greek elleipsis

First Known Use

circa 1753, in the meaning defined at sense 1a

Rhymes for ellipse

• airships
• airstrips
• clerkships
• eclipse
• equips
• filmstrips
• gunships
• judgeships
• lightships
• outstrips
• parsnips
• spaceships

Kids Definition

ellipse

noun

el·​lipse i-ˈlips 

e-

: an oval shape that is a conic section