The DSA-2000 is proposed to be a world-leading radio survey telescope and multi-messenger discovery engine for the US community. As an evolution of the 110-antenna DSA-110, the array will consist of 2000 x 5m dishes instantaneously covering the 0.7 - 2 GHz frequency range. The array will have near complete sampling of the uv-plane and will forgo a traditional correlator backend in favor of a ‘radio camera', an integrated correlator and /calibration/imaging back-end that will produce the final image data in near real-time. The algorithm and software development necessary for this paradigm shift has commenced, funded by Schmidt Futures (The Radio Camera Initiative). In a five-year prime phase, the DSA-2000 will image the entire viewable sky (~30,000 deg2) repeatedly over sixteen epochs, detecting >1 billion radio sources in a combined full-Stokes sky map with 500 nJy/beam rms noise. Continuum survey data will trace star-formation and accretion to the epoch of reionization, uniquely unaffected by dust obscuration, and will provide a new window on stellar activity and compact objects in our own Galaxy. The array will revolutionize the field of radio transients, with >105 detections per epoch, with accompanying 12-point spectro-photometry, and excellent localization for multiwavelength cross-matching. High-spectral resolution (24 kHz; ~5 km/s at 1.4 GHz) all-sky and deep field image cubes will enable resolved HI kinematics and morphologies for galaxies (including the Milky Way) out to redshift ~0.5, tracing the role of gas inflow in star formation, and probing the gaseous interface between galaxies and the IGM. The array is intended as a cornerstone for multi-messenger science. 25% of the observing time will be dedicated to timing observations of up to 200 millisecond pulsars for the detection/characterization of nano-Hertz gravitational waves from binary supermassive black holes. 5% of DSA-2000 observations will involve searching for and monitoring radio afterglows of compact object mergers detected by LIGO,Virgo, KAGRA and LIGO-India. The array will simultaneously detect and localize ~103 - 104 FRBs each year, realizing their ultimate use as cosmological tool.