A type of eclipsing binary with periods of constant (or almost constant) brightness between well-defined eclipses; abbr. EA. This feature is an indication that the system is a detached binary or semidetached binary. The secondary minimum may be invisible. Periods range from 0.2 to 10 000 days, and the amplitudes may reach several magnitudes. If mass transfer occurs, the material is accreted directly on to the hot star, not via an accretion disk. Mass transfer via an accretion disk does occur in the W Serpentis stars, which have wider separations and may be pre-Algol stars. The terms W Serpentis star and Serpentid are sometimes used to include both groups of stars.