As nouns the difference between supergiant and subgiant
is that supergiant is : A very large star having a mass between 10 and 70 solar masses while subgiant is a star that has left the main sequence but has not yet become a true giant star.
subgiant
English
Noun
(
en noun)
(astronomy) A star that has left the main sequence but has not yet become a true giant star.
Synonyms
* subgiant star