China 
Africa 
- Ripple marks
- Riprap
- Ripstop
- Rise time
- Risers
- Rising damp
- Risk
- Risk IT
- Risk appetite
- Risk assessment
- Risk aversion
- Risk factors
- Risk management
- Risk management framework
- Risk management plan
- Risk matrix
- Risk measures
- Risk modeling
- Risk perception
- Risk-adjusted net present value
- Risk-benefit analysis
- Risk-neutral
- Ritalinic acid
- Ritonavir
- Ritz method
- River bank erosion
- River channel migration
- River deltas
- River engineering
- River incision
- River island
- River mile
- River mouths
- River source
- River system
- River terraces
- Rivers
- Riveting machines
- Rivets
- Rm
- Rm-odp
- Rmsd
- Road
- Road junction
- Road pricing
- Road racing
- Road rollers
- Road surface
- Road trains
- Road-holding
- Roadheaders
- Roadrunner
- Roadworks
- Roasting
- Robocasting
- Roboethics
- Robonaut
- Robot calibration
- Robot control
- Robot fish
- Robot kinematics
- Robot learning
- Robot locomotion
- Robot navigation
- Robot software
- Robot welding
- Robot-assisted surgery
- Robotaxi
- Robotic arm
- Robotic materials
- Robotic sensors
- Robotic surgery
- Robotino
- Robots
- Robust control
- Robust decision making
- Robust decision-making
- Robust optimization
- Robust principal component analysis
- Robust regression
- Robust statistics
- Robustness
- Rocchio algorithm
- Rochelle salt
- Rock
- Rock bolts
- Rock bursts
- Rock dust
- Rock flour
- Rock formation
- Rock fragment
- Rock mass classification
- Rock shed
- Rocker arm
- Rocker-bogie
- Rocket engine
- Rocket engine nozzle
- Rocket fuel
- Rocket propellant
- Rocket sled
- Rockets
- Rockfall
- Rocks
- Rockslides
- Rockwell scale
- Rod cells
- Rod-shaped
- Rods
- Roentgen
- Rogfast
- Rogowski coil
- Rogue waves
- Rohini
- Roll bending
- Roll bonding
- Roll center
- Roll forming
- Roll trailer
- Roll-off
- Roll-to-roll
- Rollback
- Rolle's Theorem
- Roller bearings
- Roller burnishing
- Roller chain
- Roller electrospinning
- Roller mill
- Roller screw
- Rolling
- Rolling chassis
- Rolling mill
- Rolling resistance
- Rolling-element bearing
- Rollovers
- Roman aqueducts
- Roman cement
- Roman concrete
- Romanechite
- Romidepsin
- Roof
- Roof coating
- Roof gardens
- Roof pitch
- Roof shingles
- Roof tiles
- Roofing
- Roofing felt
- Roofing slate
- Rooftop solar
- Room acoustics