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 moon orbits Earth in a slight ellipse, so a full moon can sometimes be slightly closer than usual — a supermoon. —Jamie Carter, Forbes.com, 11 July 2025

The ellipse enclosing these locations is called an error ellipse. —Toshi Hirabayashi, The Conversation, 25 June 2025

Helicopters and World War II-era warplanes will fly overhead and Army parachutists will soar down to the White House's ellipse, where Trump will preside over the parade from a presidential booth. —Cybele Mayes-Osterman, USA Today, 15 June 2025

There are also plans for a parachute jump by the Army's Golden Knights at the White House ellipse. —Nik Popli, Time, 12 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