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### Definition of Oval

Date: 06/09/2002 at 20:15:44
From: Jeff McAffer
Subject: definition of an "oval"

We were recently given a book of geometrical shapes for our 7 month
old daughter (never too early for math!).  In the book there is a
drawing of an ellipse with the label "oval".  The next page has a
real world example of a chicken's egg.  We both agree that the egg is
oval (I believe this is the origin of the word) but what of the
ellipse?  So I started searching your site (very nice!) and found

http://mathforum.org/library/drmath/view/55368.html

which clearly positions ellipses as ovals.   Great.  But the
discussion raised questions as to the exact definition of "oval".

The Exeter description says:

"... This is distinct from an oval where the
perimeter has only to be a concave curve, and
there are many possibilities"

By this wording, a circle is an oval.  Something resembling a right
angle triangle with rounded corners is an oval, ...  Seems overly
broad and quite contrary to popular conception.  Is there a more
exact/narrow definition of "oval"?

Many thanks and keep up the good work.

Jeff

Date: 06/09/2002 at 23:10:26
From: Doctor Peterson
Subject: Re: definition of an "oval"

Hi, Jeff.

The word "oval" merely means "egg-shaped"; you are right that it
comes from the Latin word for "egg". It is not a precisely defined
mathematical term. If we wanted to make it more precise, we might
require these features:

continuous, smooth closed curve
convex ("concave" is a misprint on that site!)
not an exact circle
one axis of symmetry
longer along the axis than across it

An ellipse fits all but the single axis of symmetry; it is more
symmetrical than many eggs. That requirement is not always included
in defining "oval".

But because there is no mathematical gain in defining this term,
which covers a variety of figures anyway, there is no need to define
it more precisely from our perspective. We just know an "egg" when we
see it (and don't argue if someone else disagrees!).

- Doctor Peterson, The Math Forum
http://mathforum.org/dr.math/
Associated Topics:
High School Definitions
High School Euclidean/Plane Geometry
Middle School Definitions
Middle School Two-Dimensional Geometry

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