R R-Value Radar Radiation Radio Radio and Television Interference Noise Radio Astronomy Radio Frequency Radio Frequency Interference - Neas Letter Radioactivity Rankine Cycle RARP Raster Data Rates - Residential Reactance Reactive Power Rectifier References Reflection Refraction Refrigeration Relativity Relay Relay - Advantages To Simultaneous Fast Clearing Remote Terminal Unit (RTU) Repeater Resin Resistance Resistor Rest Mass Reverse Address Resolution Protocol (RARP) Right Angle Rosetta Stone RTU Rubber Rutherford, Ernest