China 
Africa 
- Rheumatic fever
- Rheumatism
- Rheumatoid arthritis
- Rheumatoid factor
- Rhinitis
- Rhinorrhea
- Rhizobacteria
- Rhizobia
- Rhizobium leguminosarum
- Rhizome
- Rhizomucor miehei
- Rhizosphere
- Rho
- Rhodamine
- Rhodamine 123
- Rhodamine 6g
- Rhodamine B
- Rhodanese
- Rhodium
- Rhodium acetate
- Rhodium(II) acetate
- Rhodobacter capsulatus
- Rhodobacter sphaeroides
- Rhodobacterales
- Rhodochrosite
- Rhodococcus opacus
- Rhodonite
- Rhodopseudomonas palustris
- Rhodopsin
- Rhombohedral
- Rhomboid
- Rhombus
- Rhyodacite
- Rhyolite
- Rhythmite
- Ri plasmid
- Rib cage
- Rib fractures
- Ribavirin
- Ribbon cables
- Ribitol
- Riboflavin
- Ribonuclease
- Ribonuclease A
- Ribonucleoprotein
- Ribonucleotide reductase
- Ribonucleotides
- Ribose
- Ribose 5-phosphate
- Ribosomal DNA
- Ribosomal RNA
- Ribosomal proteins
- Ribosome binding site
- Ribosome biogenesis
- Ribosome-binding site
- Ribosomes
- Ribs
- Ribulose
- Ribulose 5-phosphate
- Riccati equation
- Rice bran wax
- Rice hulls
- Rich text
- Richards equation
- Richardson extrapolation
- Rician fading
- Ricin
- Ricinine
- Ricinoleic acid
- Rickets
- Rickettsia
- Rickettsia rickettsii
- Rickettsiaceae
- Rickshaws
- Ride height
- Ride quality
- Ride-through
- Ridge detection
- Ridge push
- Ridge regression
- Ridges
- Riebeckite
- Riemann Invariant
- Riemann integral
- Riemann mapping theorem
- Riemann problem
- Riemann solver
- Riemann sphere
- Riemann sum
- Riemann surfaces
- Riemannian geometry
- Riemannian manifolds
- Riesz Representation Theorem
- Riesz space
- Rietveld refinement
- Rifampicin
- Riffles
- Rift valleys
- Rift zones
- Rifts
- Right angles
- Right ascension
- Right atrium
- Right coronary artery
- Right half-plane
- Right hepatic artery
- Right to be forgotten
- Right to explanation
- Right upper quadrant
- Right-hand rule
- Right-handed
- Right-to-left shunt
- Rigid body
- Rigid origami
- Rigid rotor
- Rigid transformation
- Rigid-frame bridge
- Rigidity
- Rigidity theory
- Rigor
- Rigour
- Rill
- Rimantadine
- Rime ice
- Rims
- Ring
- Ring counter
- Ring expansion
- Ring gear
- Ring homomorphism
- Ring laser
- Ring laser gyroscope
- Ring network
- Ring of integers
- Ring oscillator
- Ring signatures
- Ring spinning
- Ring strain
- Ring vaccination
- Ring-closing metathesis
- Ring-opening polymerization
- Ringing
- Ringtones
- Ringworm
- Rip currents
- Riparian
- Riparian buffer
- Riparian zones
- Ripple
- Ripple effect