Illustration of ellipse
- F F' foci
- P P' P'' any point on the curve
- FP + PF' = FP'' + P''F' = FP' + P'F'
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
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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
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The double-ellipse frame now reveals the full architecture of the caliber DR002SR, while the watch preserves the classical proportions and architecture of the original.
—
Luisa Zargani, Footwear News, 19 Jan. 2026
In our seminar, Bolin later showed a visualization of 3I/ATLAS's orbit around the galaxy — no neat ellipse, but rather a looping, spiraling path distorted by encounters with gas clouds, spiral arms and dark matter.
—Kenna Hughes-Castleberry, Space.com, 2 Dec. 2025
Since the moon’s orbit around the Earth is not a perfect circle but rather an ellipse or oval, the moon’s distance from Earth can vary in its orbit, but not all that much.
—Mike Lynch, Twin Cities, 5 Oct. 2025
These can be defined mathematically, with the key factor being the eccentricity: how much the ellipse deviates form a circle.
—Phil Plait, Scientific American, 25 July 2025
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Luisa Zargani, Footwear News, 19 Jan. 2026
In our seminar, Bolin later showed a visualization of 3I/ATLAS's orbit around the galaxy — no neat ellipse, but rather a looping, spiraling path distorted by encounters with gas clouds, spiral arms and dark matter.
—Kenna Hughes-Castleberry, Space.com, 2 Dec. 2025
Since the moon’s orbit around the Earth is not a perfect circle but rather an ellipse or oval, the moon’s distance from Earth can vary in its orbit, but not all that much.
—Mike Lynch, Twin Cities, 5 Oct. 2025
These can be defined mathematically, with the key factor being the eccentricity: how much the ellipse deviates form a circle.
—Phil Plait, Scientific American, 25 July 2025
See All Example Sentences for ellipse
Cite this Entry
“Ellipse.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/ellipse. Accessed 21 Jan. 2026.
Copy CitationKids Definition
ellipse
noun
el·lipse
i-ˈlips 
e-
: an oval shape that is a conic section
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