Africa 
China 
Japan 
MENA 
- Jordan algebra
- Jordan block
- Jordan matrix
- Jordan normal form
- Josephson effect
- Josephson junctions
- Joule
- Joule effect
- Joule heating
- Joule-Thomson effect
- Joysticks
- Juan de Fuca Plate
- Judgments
- Juglone
- Jugular vein
- Julia
- Julia set
- Jumbo frames
- Jump seats
- Jumpers
- Juncker Plan
- Junction box
- Junction temperature
- Junction tree algorithm
- Junctional epidermolysis bullosa
- Junctional epithelium
- Junctions
- Jupiter Europa Orbiter
- Jurkat cells
- Jute
- Juvenile
- Juvenile hormone
- Juvenile idiopathic arthritis
- Juxtacrine
- Juxtaglomerular cells
- K band
- K factor
- K nearest neighbors
- K-alpha
- K-casein
- K-complex
- K-d trees
- K-distribution
- K-edge
- K-epsilon turbulence model
- K-factor
- K-homology
- K-means clustering
- K-means++
- K-medoids
- K-mer
- K-nearest neighbors algorithm
- K-omega turbulence model
- K-space
- K-svd
- K-theory
- K-tree
- K562
- K562 cells
- KBS-3
- KDC
- KDF
- KEGG
- KERS
- KGF
- KLH
- KM
- KML
- KNIME
- KPI
- KRAS
- KSTAR
- KVM
- Kaempferol
- Kaersutite
- Kahweol
- Kaiser window
- Kaldi
- Kali
- Kali Linux
- Kalina cycle
- Kallikrein
- Kalman decomposition
- Kalman filter
- Kalsilite
- Kamacite
- Kambalda
- Kames
- Kanamycin
- Kanban
- Kankar
- Kanthal
- Kaolin
- Kaolinite
- Kapitza resistance
- Kaplan turbines
- Kappa
- Kapton
- Karaya gum
- Karel
- Karl Fischer titration
- Karnaugh maps
- Karst
- Karst plateau
- Karst springs
- Karyotype
- Kasumi
- Katz centrality
- Kauri-butanol value
- Kava
- Kavalactones
- Kawabata Evaluation System
- Kawasaki disease
- Kaya Identity
- Keap1
- Keel
- Keepalive
- Keggin structure
- Keloid
- Kelvin
- Kelvin equation
- Kelvin probe force microscope
- Kelvin waves
- Ken
- Kendall rank correlation coefficient
- Kendall's W
- Kendall's notation
- Kenyaite
- Kepler
- Kepler problem
- Keras
- Keratin
- Keratin-associated proteins
- Keratinase
- Keratinocytes
- Keratitis
- Keratoconjunctivitis
- Keratoconus
- Keratometer
- Keratometry
- Keratomileusis
- Keratophyre
- Keratoprosthesis
- Kerbside collection
- Kerckhoffs's principle
- Kerley lines
- Kerma
- Kermes
- Kermesite
- Kernel