Are there any differences between "oval" and "ellipse"?
I believe they can be used interchangeably in common English, but have specific (and different) meanings when used in mathematics.
The online Cambridge dictionary contains the following definitions:
However, in geometry there is a difference. According to the Wikipedia page on ovals:
In addition, from the Math Forum
This is adapted from my answer to another question.
In my experience, "ellipse" usually has a precise, geometric meaning, while "oval" is a more vague and general term. Most dictionaries I've checked agree with this, but a few dictionaries say that the two words can be used interchangeably. The New Oxford American Dictionary defines "oval" as "having a rounded and slightly elongated outline or shape, like that of an egg". It defines "ellipse" as "a regular oval shape, traced by a point moving in a plane so that the sum of its distances from two other points (the foci) is constant".
Various other online sources agree:
Mathworld agrees: oval
mathforum.org agrees: "Simply, an ellipse IS an oval, but an oval may or may not be an ellipse."
answers.com agrees: "An ellipse always has two axes of reflection; an oval has one or more."
I've found a relatively few sources which define "ellipse" and "oval" to mean the same thing. I've found no sources at all which say that "ellipse" is more general than "oval".
From what I can tell (looking at my kids' Montessori curriculum), an ellipse is a kind of oval. An ellipse does not have a "pointier" end (is not like an egg), whereas an oval can be pointier at one end, or not.
To me the defining difference is this:
An oval can be made from two radiuses. That is, you can make an oval using your compass (or parts of a circle, if you like). You can never do this with an ellipse. That is, no part of an ellipse will ever make a circle.
protected by tchrist Feb 26 at 1:18
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