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A member of a group of stars, mainly of spectral type F, G or K, which, when classified according to standard criteria, form a sequence just below (or to the left of) the main sequence on the Hertzsprung-Russell diagram. These stars have exceptionally low abundances of the heavier elements, compared with the Sun, and belong to the so-called Population II of older, "metal"-deficient stars. The absorption lines in their spectra are relatively weak and, because most such lines occur in the blue and ultraviolet part of the spectrum, the subdwarfs look bluer in colour than their counterparts with solar-like abundances.
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