What primarily distinguishes a giant star from a dwarf star of the exact same surface temperature?

Answer

It has a substantially larger radius and greater luminosity

A giant star is defined by having a vastly larger physical size (radius) and consequently a much higher light output (luminosity) compared to a main-sequence dwarf star, even if they share the identical surface temperature.

What primarily distinguishes a giant star from a dwarf star of the exact same surface temperature?
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