China 
Africa 
- Skip lesions
- Skull
- Skull fracture
- Slapped cheek syndrome
- Sleep
- Sleep and memory
- Sleep and metabolism
- Sleep apnea
- Sleep apnea syndrome
- Sleep cycle
- Sleep debt
- Sleep deprivation
- Sleep diary
- Sleep disorders
- Sleep efficiency
- Sleep hygiene
- Sleep inertia
- Sleep latency
- Sleep onset
- Sleep onset latency
- Sleep paralysis
- Sleep sex
- Sleep spindles
- Sleep state misperception
- Sleep study
- Sleep tracking
- Sleep-learning
- Sleep-related breathing disorder
- Sleeping position
- Sleeping sickness
- Sleepwalking
- Sleeve gastrectomy
- Slime layer
- Slings
- Slip-Slop-Slap
- Slipped capital femoral epiphysis
- Slipped strand mispairing
- Slit
- Slit lamp
- Sloan letters
- Sloping forehead
- Slow afterhyperpolarization
- Slow code
- Slow wave sleep
- Slow-wave sleep
- Sludge
- Sluggish schizophrenia
- Slurred speech
- Sly syndrome
- Smad proteins
- Smad1
- Small
- Small GTPases
- Small Incision Lenticule Extraction
- Small Maf
- Small RNAs
- Small cell lung cancer
- Small fiber neuropathy
- Small fiber peripheral neuropathy
- Small for gestational age
- Small heterodimer partner
- Small interfering RNA
- Small intestine
- Small intestine cancer
- Small molecule
- Small molecules
- Small nuclear RNA
- Small nuclear ribonucleoprotein
- Small nucleolar RNA
- Small population size
- Small proteins
- Small ribosomal subunit
- Small saphenous vein
- Small subunit ribosomal RNA
- Small-cell lung cancer
- Smallpox
- Smallpox vaccine
- Smallpox virus
- Smart fabric
- Smart textiles
- Smartglasses
- Smear layer
- Smectite
- Smegma
- Smell
- Smell training
- Smilax aristolochiifolia
- Smilax glabra
- Smiley
- Smith Lemli Opitz Syndrome
- Smith Magenis Syndrome
- Smith-Lemli-Opitz Syndrome
- Smith-Magenis syndrome
- Smog
- Smoke
- Smoke inhalation
- Smoked food
- Smoked foods
- Smokeless tobacco
- Smoker's macrophages
- Smoking
- Smoking age
- Smoking bans
- Smoking cessation
- Smoking-related interstitial fibrosis
- Smooth endoplasmic reticulum
- Smooth muscle
- Smooth muscle actin
- Smooth muscle cells
- Smooth muscle tumour
- Smooth pursuit
- Smooth pursuit eye movement
- Smouldering myeloma
- Snake venom
- Snap freezing
- Snapping hip syndrome
- Snare protein
- Snarl
- Sneathia
- Sneddon's syndrome
- Sneeze
- Sneezing
- Snellen chart
- Sniffing
- Snoezelen
- Snoring
- Snout reflex
- Snow blindness
- Soap
- Soap scum
- Soap substitutes
- Sober living house
- Sobriety
- Social Cognition and Interaction Training
- Social Hygiene Movement
- Social Interaction Anxiety Scale
- Social Phobia Inventory
- Social Readjustment Rating Scale
- Social Role Valorization
- Social Stories
- Social anxiety
- Social anxiety disorder
- Social cognition
- Social cognitive theory
- Social cohesion
- Social competence
- Social concept
- Social connectedness
- Social construction
- Social constructivism