China 
Africa 
- Renin-angiotensin system
- Rennet
- Renormalization
- Renormalization group
- Renovascular hypertension
- Rent-seeking
- Rep
- RepRap
- Repairability
- Repast
- Repeat unit
- Repeatability
- Repeated game
- Repeated incremental pruning to produce error reduction
- Repeated measures design
- Repeater
- Repeater insertion
- Reperfusion injury
- Repertory grid
- Repetitive control
- Replace
- Replay attacks
- Replica plating
- Replicas
- Replication
- Replication stress
- Replicator equation
- Replisome
- Repointing
- Repolarization
- Reporter gene
- Reporting bias
- Repository
- Repowering
- Representation
- Representation theorem
- Representation theory
- Representations
- Representative elementary volume
- Representative volume element
- Representer theorem
- Repressors
- Reprocessed uranium
- Reproducibility
- Reproductive medicine
- Reproductive success
- Reproductive system
- Reproductive technology
- Reproductive toxicity
- Reprogramming
- Reprojection error
- Reptation
- Reputation systems
- Requirement
- Requirement diagram
- Requirements analysis
- Requirements elicitation
- Requirements engineering
- Requirements management
- Requirements traceability
- Resampling
- Resazurin
- Rescaled range
- Rescue effect
- Rescue robot
- Research reactors
- Resection
- Resection margin
- Reservation price
- Reserved words
- Reservoir computing
- Reservoir engineering
- Reservoir modeling
- Reservoir sampling
- Reservoir simulation
- Reservoirs
- Residence time
- Residential care
- Residential gateway
- Residual
- Residual entropy
- Residual gas analyzer
- Residual neural network
- Residual strength
- Residual stress
- Residual sum of squares
- Residuals
- Residue
- Residue theorem
- Residuum
- Resilience
- Resilience engineering
- Resin
- Resin acids
- Resin casting
- Resistance
- Resistance curve
- Resistance thermometers
- Resistance wire
- Resistant starch
- Resistin
- Resistive pulse sensing
- Resistivity
- Resistome
- Resistor
- Resolvers
- Resonance
- Resonance Raman spectroscopy
- Resonance ionization
- Resonant column test
- Resonant converter
- Resonant inductive coupling
- Resonant inelastic x-ray scattering
- Resonant interaction
- Resonant inverter
- Resonant tunneling diode
- Resonant ultrasound spectroscopy
- Resonant-tunneling diode
- Resonators
- Resorcinarene
- Resorcinol-formaldehyde
- Resource
- Resource allocation
- Resource consumption
- Resource contention
- Resource depletion
- Resource efficiency
- Resource intensity
- Resource management
- Resource productivity
- Respiration rate
- Respiratory acidosis
- Respiratory alkalosis
- Respiratory arrest
- Respiratory burst
- Respiratory depression
- Respiratory droplets
- Respiratory epithelium
- Respiratory exchange ratio
- Respiratory failure
- Respiratory quotient
- Respiratory rate
- Respiratory sounds
- Respiratory system
- Respiratory tract
- Respiratory tract infections
- Respirometry
- Response amplitude operator
- Response bias
- Response factor