* Radius: How big a star is across. This can range from tiny neutron stars (about 10 miles) to supergiants (hundreds of times the size of our Sun).

* Mass: How much a star weighs. Stars can be as small as a tenth the mass of our Sun or over 100 times more massive.

* Luminosity: How bright a star is. This is a measure of the energy a star emits, and is related to both size and temperature.

Could you tell me what aspect of a star's size you're interested in?