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Africa 
- Knickpoint
- Knife
- Knitr
- Knitted fabric
- Knitting
- Knitting machines
- Knitwear
- Knobs
- Knock-in
- Knockdown
- Knockout
- Knockout mouse
- Knoevenagel condensation
- Knoop hardness test
- Knot density
- Knot invariants
- Knot theory
- Knots
- Knowledge acquisition
- Knowledge base
- Knowledge engineering
- Knowledge graphs
- Knowledge integration
- Knowledge management
- Knowledge organization
- Knowledge organization system
- Knowledge representation
- Knowledge representation and reasoning
- Knowledge society
- Knowledge space
- Knowledge value chain
- Knowledge-based authentication
- Knowledge-based engineering
- Knowledge-based system
- Known-plaintext attack
- Knuckles
- Knudsen cell
- Knudsen diffusion
- Knudsen equation
- Knudsen layer
- Knudsen number
- Knurled
- Knurling
- Koch Snowflake
- Kohn anomaly
- Kojic acid
- Kola nut
- Kolmogorov complexity
- Komatiite
- Kombucha
- Kondo effect
- Kondo insulators
- Kondo model
- Koobface
- Koopmans' theorem
- Korotkoff sounds
- Kosmotropic
- Kosterlitz-Thouless transition
- Kotlin
- Kovac's reagent
- Kovar
- Krafft temperature
- Kraft paper
- Kraft process
- Kramers-Kronig relations
- Kraton
- Krennerite
- Kriging
- Kripke semantics
- Kroll process
- Kronecker delta
- Kronecker product
- Kronecker symbol
- Kruithof curve
- Krylov subspace
- Krypton
- Krypton-85
- Krytox
- Kt
- Kubelka-Munk theory
- Kubernetes
- Kudankulam Nuclear Power Plant
- Kukersite
- Kunlun Fault
- Kupffer cells
- Kurtosis
- Kutta condition
- Kyanite
- Kynurenic acid
- Kynurenine
- Kynurenine pathway
- Kyropoulos method
- L band
- L-BFGS
- L-DOPA
- L-estimator
- L-functions
- L-glucose
- L-moments
- L-shell