Short for Double Data Rate, the spec family for the standard DRAM that plugs into PC and server boards. Each generation (DDR4 to DDR5) improves speed and density. Together with LPDDR (the low-power mobile spec) and HBM (stacked next to GPUs), it forms one of DRAM's three main product families. Server DDR5 module prices are a widely quoted thermometer for data center demand.