DSLR
A digital single-lens reflex camera: an SLR body with a sensor in place of film, retaining the mirror and optical viewfinder.
In depth
DSLRs dominated professional work from roughly 2003 to 2018 because they inherited decades of lens systems and delivered an optical finder with no lag or battery drain. Their structural limits — mirror slap, a separate phase-detect module needing calibration, and the flange distance the mirror demands — are exactly what mirrorless designs removed.
Examples in practice
A press photographer shooting 10,000 frames a day valued a DSLR's optical finder for tracking a runner without any electronic delay.