- Rechallenge
- Recidivism
- Reciprocal altruism
- Reciprocal cross
- Reciprocal determinism
- Reciprocal inhibition
- Reciprocal translocation
- Reciprocity
- Recklessness
- Recognition
- Recognition memory
- Recognition sequence
- Recombinant DNA
- Recombinant DNA technology
- Recombinant antibodies
- Recombinant factor VIIa
- Recombinant gene
- Recombinant human parathyroid hormone
- Recombinant proteins
- Recombinant vaccine
- Recombinant virus
- Recombinase
- Recombinase polymerase amplification
- Recombinases
- Recombination
- Recombination repair
- Recombination signal sequences
- Recombination-activating gene
- Recombineering
- Recommended dietary allowances
- Reconciliation
- Reconsolidation
- Reconstruction
- Reconstructive ladder
- Reconstructive surgery
- Recoverin
- Recovery model
- Recovery position
- Recreational drugs
- Recreational therapist
- Recreational therapy
- Recrudescence
- Rectal
- Rectal administration
- Rectal ampulla
- Rectal bleeding
- Rectal cancer
- Rectal examination
- Rectal foreign body
- Rectal pain
- Rectal prolapse
- Rectal temperature
- Rectal tenesmus
- Rectal thermometer
- Rectal thermometry
- Rectal varices
- Rectal venous plexus
- Rectification
- Recto uterine pouch
- Rectoanal inhibitory reflex
- Rectocele
- Rectouterine pouch
- Rectovaginal examination
- Rectovaginal fascia
- Rectovaginal fistula
- Rectovaginal septum
- Rectus abdominis
- Rectus abdominis muscle
- Rectus capitis lateralis
- Rectus capitis posterior major
- Rectus capitis posterior minor
- Rectus capitis posterior minor muscle
- Rectus femoris
- Rectus femoris muscle
- Rectus sheath
- Rectus sheath hematoma
- Recurrent corneal erosion
- Recurrent laryngeal nerve
- Recurrent miscarriage
- Recurrent nevi
- Recurrent pyogenic cholangitis
- Recurrent respiratory papillomatosis
- Recursive partitioning
- Red blood cell
- Red blood cell distribution width
- Red blood cell indices
- Red cell distribution width
- Red complex
- Red eye
- Red fluorescent protein
- Red hair
- Red meat
- Red pulp
- Red raspberry leaf
- Red reflex
- Red ribbon
- Redistribution
- Redox couple
- Redox gradient
- Redox indicator
- Redox reactions
- Reduced nicotinamide adenine dinucleotide
- Reducing agents
- Reducing environment
- Reducing sugar
- Reducing sugars
- Reductases
- Reduction
- Reductionism
- Reductive stress
- Redundancy
- Reduplicative paramnesia
- Reduviidae
- Reed-Frost model
- Reed-Sternberg cells
- Reeler
- Reelin
- Reentry
- RefSeq
- Refacto
- Refeeding syndrome
- Reference dose
- Reference genome
- Reference material
- Reference range
- Referral
- Referred pain
- Refinery
- Reflectance
- Reflection
- Reflection coefficient
- Reflective listening
- Reflectivity
- Reflex
- Reflex arcs
- Reflex bradycardia
- Reflex hammer
- Reflex seizures
- Reflexes
- Reflexology
- Reflux
- Reflux condenser
- Reflux esophagitis
- Reflux nephropathy
- Refraction
- Refraction index
- Refractive error
- Refractive errors
- Refractive index
- Refractive surgery