- ionic breakdown
- ionic strength
- ionise
- ionize
- irradiancy
- irradiation
- irreflexive relation
- isentropic
- inward flux
- iodine flask
- ion pair
- ion source
- ion spectrum
- ionic binding
- ionic bond
- ionic conductance
- ionic polarization
- ionic radius
- ionization source
- irradiance
- irradiate
- irradiated
- irradiation chamber
- irreflective relation
- irreversible shutdown
- irrotaional field
- irrotational flow
- isentropic compressibility
- isochoric
- isochromatic
- isoclinal line
- isoelectric
- isoenergetic
- isolated system
- isolating valve
- isomeric transition
- isotherm
- isothermal compressibility
- isothermal expansion
- isothermal tube
- isotope number
- isotopic abundance
- isotopic analysis
- isotropic turbulence
- Jackson model
- joint ring
- Jost function
- just scale
- K-state
- kation
- kernel
- jack
- jammer
- jaw crusher
- jet propulsion
- jig table
- Jodel detector
- kampometer
- kathode
- kenotron
- keV
- key light
- key signature
- Keyes equation
- jeweled
- jig
- Kelvin equation
- kerma rate
- khaki goo
- kinematic
- kinematics
- kinetic friction
- kinetic separation
- kinetic spectrophotometry
- kinetic temperature
- king journal
- kjeldahl method
- Knight shift
- karyolisis
- keynote
- kickback
- Kikuchi line
- kinematic method
- kinematical
- klystron
- Kruskal limit
- labile
- lability
- laboratory reactor
- laboratory standard
- laboratory stool
- lag
- lag element
- Lagrangian multiplier
- Lagrangian operator
- Lagrangian viewpoint
- kodachrome process
- Kossel line
- labeling
- labeling technique