Definition:Ellipse/Eccentricity

Definition

Let $K$ be the ellipse specified as the locus of points $P$ to a straight line $D$ and a point $F$ such that $PD$ and $PF$ are related by the condition:

$\size {PF} = e \size {PD}$

where $0 < e < 1$.

The constant $e$ is known as the eccentricity of the ellipse.

Also denoted as

Some sources use $\epsilon$ for the eccentricity of a conic section.

Also see

• Definition:Directrix of Ellipse
• Definition:Focus of Ellipse
• Definition:Focus-Directrix Property of Ellipse

• Results about the eccentricity of an ellipse can be found here.

Sources

• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): conic (conic section)
• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): ellipse
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): conic (conic section)
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): ellipse