China 
Africa 
- Reactive centrifugal force
- Reactive diluent
- Reactive dyes
- Reactive intermediates
- Reactive ion etching
- Reactive materials
- Reactive nitrogen
- Reactive power
- Reactive sulfur species
- Reactive-ion etching
- Reactivity
- Reactivity series
- Reactor core
- Reactor pressure vessels
- Reactor protection system
- Reactor-grade plutonium
- Read
- Read-only
- Reading frames
- Readout integrated circuit
- Reads
- Ready-mix concrete
- Reagent bottles
- Reagents
- Real algebraic geometry
- Real analysis
- Real estate developers
- Real estate development
- Real gas
- Real image
- Real line
- Real number
- Real projective plane
- Real world data
- Real-Time Transport Protocol
- Real-time
- Real-time Java
- Real-time business intelligence
- Real-time communication
- Real-time control system
- Real-time data
- Real-time database
- Real-time polymerase chain reaction
- Real-time simulation
- Real-time transcription
- Real-valued function
- Realgar
- Reality
- Reamers
- Rear-end collision
- Rear-wheel drive
- Reasoning system
- ReaxFF
- Rebar
- Rebaudioside A
- Reboiler
- Reboot
- Rebound effect
- RecA
- Recall bias
- Received noise power
- Receiver
- Receptive fields
- Receptor
- Receptor antagonist
- Receptor modulators
- Receptor potentials
- Rechargeable battery
- Reciprocal
- Reciprocal altruism
- Reciprocal inhibition
- Reciprocal innervation
- Reciprocal lattice
- Reciprocal length
- Reciprocating compressor
- Reciprocating engines
- Reciprocating motion
- Reciprocating pump
- Reciprocating saw
- Reciprocity
- Recirculating aquaculture system
- Reclaimed water
- Recloser
- Recoating
- Recoil
- Recombinant
- Recombinant DNA
- Recombinant antibodies
- Recombinant virus
- Recombinase
- Recombinase polymerase amplification
- Recombination
- Recommender systems
- Reconfigurability
- Reconfigurable antenna
- Reconfigurable computing
- Reconfigurable manufacturing systems
- Reconstruction
- Reconstruction filter
- Reconstructive surgery
- Reconvergent fan-out
- Record
- Record linkage
- Recording
- Recording head
- Records
- Recovery
- Recovery boiler
- Recovery position
- Recovery room
- Recreational mathematics
- Recrystallization
- Rectal
- Rectal pain
- Rectangle
- Rectangular cuboid
- Rectangular function
- Rectangular lattice
- Rectangular potential barrier
- Rectenna
- Rectification
- Rectifier
- Rectilinear polygon
- Rectisol
- Rectus abdominis
- Rectus abdominis muscle
- Rectus femoris
- Rectus femoris muscle
- Rectus sheath
- Recuperator
- Recurrence period density entropy
- Recurrence plots
- Recurrence quantification analysis
- Recurrence relation
- Recurrent laryngeal nerve
- Recurrent neural networks
- Recursion
- Recursive Bayesian estimation
- Recursive definition
- Recursive filter
- Recursive neural network
- Recursive partitioning
- Recursively enumerable
- Recycled cotton
- Recycled fuel
- Recycled paper
- Recycled wool
- Recycling
- Recycling rate
- Red Sea Rift