What does ellipse mean?
An ellipse is a smooth, closed oval curve defined mathematically as the set of all points in a plane for which the sum of the distances to two fixed points, called the foci, remains constant. In everyday terms, it is simply an elongated or flattened circle. Ellipses are central to geometry and physics: Johannes Kepler established in the early 17th century that planets orbit the sun along elliptical paths, a discovery that reshaped astronomy. Beyond mathematics, the word describes any oval shape in art, architecture, engineering, and design, where elliptical arches, mirrors, and tracks are common. The term carries a precise, technical register but is readily understood by general readers thanks to its familiar oval appearance. It derives from the Greek elleipsis, meaning "falling short," because a conic section cut at a shallow angle falls short of forming a full circle. Related forms include the adjective "elliptical" and the adverb "elliptically." Note that the word is easily confused with "ellipsis," the punctuation mark indicating omitted text.
nounA regular oval shape traced by a point moving in a plane so that the sum of its distances from two fixed points (the foci) is constant; more generally, a closed curve resembling a flattened or elongated circle.
- A closed oval plane curve such that the sum of the distances from any point on it to two fixed points (foci) is constant.
- A shape or figure resembling such a curve; an oval.
"The planets travel around the sun in ellipses rather than perfect circles."
"The architect designed the plaza around a vast granite ellipse."
"Kepler demonstrated that Mars moves in an ellipse, not a circle."
Pronounced /ɪˈlɪpsiːz/, identical in spelling to the plural of "ellipsis" but stressed on the second syllable.
"The orbits of the inner planets are nearly circular ellipses."
Every planet in our solar system travels in an ellipse — Kepler figured this out in 1609, and it's why no orbit is ever a perfect circle.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of ellipse
"Ellipse" entered English in the early 17th century, borrowed from French ellipse, which traces back to Latin ellipsis and ultimately to the Greek elleipsis, meaning "a falling short, omission." The Greek root is en- ("in") plus leipein ("to leave, fail"), the same verb that gives us "ellipsis" and "eclipse." The geometric sense arose because a conic section cut obliquely "falls short" of becoming a complete circle. Cognates sharing this root include "elliptical," "ellipsis," and "paralipsis."
Related word forms
How ellipse is actually used
"Ellipse" is a neutral, largely technical term common in mathematics, astronomy, and design. It is always pronounced with stress on the second syllable, unlike "ellipsis," which stresses the first — a frequent source of mispronunciation. The plural is "ellipses" (pronounced /ɪˈlɪpsiːz/), identical in spelling to the plural of "ellipsis." The verb form is rare; the adjective "elliptical" is the usual derived form, though "elliptic" also occurs in mathematical contexts.
Easily confused with ellipse
An ellipse is an oval geometric curve, while an ellipsis (plural ellipses) is the omission of words in speech or writing, often marked by three dots (...).
An eclipse is the obscuring of one celestial body by another, whereas an ellipse is an oval-shaped curve; the two merely rhyme and share Greek roots.