In general, an imperfect cadence in a minor key, but more precisely an imperfect cadence on the dominant chord of the relative minor using the first inversion of the subdominant chord (IVb-V). This is a Renaissance device still used in late-Baroque by composers like Corelli, Handel and Bach. It was generally used at the end of the slow movement (in relative minor) of sonata or concertos written in major keys providing a (iii to I) tonal switch with the start of the following movement [in a major key].