China 
Africa 
- Radicals
- Radio
- Radio access technology
- Radio astronomy
- Radio beacon
- Radio broadcasting
- Radio communication service
- Radio control
- Radio frequency induction
- Radio modem
- Radio navigation
- Radio networks
- Radio noise
- Radio occultation
- Radio propagation
- Radio receivers
- Radio scanner
- Radio sources
- Radio spectrum
- Radio telescopes
- Radio waves
- Radio-controlled boats
- Radio-frequency identification
- Radio-frequency induction
- Radio-frequency microelectromechanical system
- Radioactive
- Radioactive contamination
- Radioactive decay
- Radioactive iodine
- Radioactive sources
- Radioactive tracers
- Radioactive waste
- Radioactive waste disposal
- Radiobiology
- Radiocarbon dating
- Radiochemistry
- Radiocontrast
- Radioecology
- Radiofrequency ablation
- Radiogenic
- Radioimmunoassay
- Radioimmunotherapy
- Radiolabelled
- Radioligand
- Radiolocation
- Radiological
- Radiology
- Radioluminescence
- Radiolysis
- Radiometric
- Radiometric calibration
- Radiometry
- Radiomics
- Radionuclide angiography
- Radionuclide generator
- Radionuclides
- Radiopaque
- Radiopharmaceuticals
- Radiopharmacology
- Radiopharmacy
- Radioresistance
- Radioresistant
- Radiosensitivity
- Radiosensitizer
- Radiosity
- Radiosondes
- Radiosurgery
- Radiosynthesis
- Radium
- Radium compounds
- Radium sulfate
- Radium-223
- Radius
- Radius of convergence
- Radius of curvature
- Radius of gyration
- Radix
- Radix sort
- Radomes
- Radon
- Radon transform
- Radon-222
- Raffinate
- Raffinose
- Rafters
- Raglan Mine
- Ragone chart
- Ragone plot
- Ragweed
- Rail grinding
- Rail profile
- Rail transport
- Railgun
- Rails
- Railway
- Railway brake
- Railway electrification
- Railway engineering
- Rain gardens
- Rain shadow
- Rainbow tables
- Rainbowing
- Rainfall simulator
- Rainflow-counting algorithm
- Rainforests
- Rainscreen
- Rainwater harvesting
- Rainwater tank
- Raise
- Raised beach
- Raised floor
- Raised-cosine filter
- Raising
- Rake
- Rake angle
- Rake receiver
- Ralstonia solanacearum
- Ram pressure
- Raman amplification
- Raman laser
- Raman microscopy
- Raman scattering
- Raman spectroscopy
- Ramjet
- Rammed earth
- Ramp function
- Ramp-up
- Rams
- Ramsdellite
- Ran
- Rancid
- Random Access
- Random assignment
- Random coils
- Random dopant fluctuation
- Random effects model
- Random fields
- Random forests
- Random geometric graphs
- Random graphs
- Random laser
- Random matrices
- Random matrix
- Random measure
- Random mixture
- Random modulation
- Random number
- Random optimization
- Random oracle
- Random permutation