thumb|The [[Hertzsprung–Russell diagram showing the location of main sequence dwarf stars and white dwarfs]]
A dwarf star is a star of relatively small size and low luminosity. All main-sequence stars are dwarf stars. The meaning of the word "dwarf" was later extended to some star-sized objects that are not stars, and some types of the compact stellar remnants.
History
The term was originally coined in 1906 when the Danish astronomer Ejnar Hertzsprung noticed that the reddest stars – classified as K and M in the Harvard scheme – could be divided into two distinct groups. They are either much brighter than the Sun, or much fainter. To distinguish these groups, he called them "giant" and "dwarf" stars,