What are the units used for eccentricity?

Question

Thanks if you can help =)

Answer 1

Just to reassure you about the previous answers - eccentricity has no units.

You should ask your teacher what units he/she thinks it has.

You can look it up in wikipedia for the official definition

(Ellipse#Eccentricity)

- but since it is a ratio, it should not have units

Answer 2

Eccentricity itself has no unit (that I have ever heard of), but your lab may have wanted you to calculate a change in distance (feet, meters, etc.) or an angle (degrees, radians).

Answer 3

Eccentricity as in Kepler, orbits, and ellipses is unitless and lies above and including 0 and below 1.

e=0 => Circle

e~1 => Long thin ellipse