A type of pulsating variable with a short period (0.01–0.2 day) and small amplitude (0.003–0.9 mag.); abbr. DSCT. The pulsation is driven primarily by instabilities in the hydrogen convection zone, and multiple pulsation modes occur simultaneously. These Population I stars have spectral types from A0 to F5 and lie at the lower end of the Cepheid instability strip, either on the main sequence or among the subgiants and giants. Those with amplitudes greater than 0.1 mag. are often termed high-amplitude Delta Scuti stars (HADS), while those with smaller amplitudes are low-amplitude Delta Scuti stars (LADS). The high-amplitude stars have well-defined period-luminosity relations and are useful for distance measurements. In older literature, Delta Scuti stars were often described by the misleading terms dwarf Cepheid, RRs variable, or ultra-short-period variable. See also Ai Velorum Star; Sx Phoenicis Star.