- Furniture
- Furring
- Fuse plugs
- Fused quartz
- Fuselage
- Fusible alloy
- Fusion power
- Fusion welding
- G-10
- GDI
- GFRC
- GGBFS
- GGG
- GIS
- GPC
- GPR
- GPU
- GTAW
- GUI
- Gabaa receptor
- Gabbro
- Gabions
- Gadolinium
- Gahnite
- Galena
- Galinstan
- Gallic acid
- Galling
- Gallium
- Gallium arsenide
- Gallium fluoride
- Gallium nitrate
- Gallium nitride
- Gallium oxide
- Gallium phosphide
- Galvanic anodes
- Galvanic cells
- Galvanic corrosion
- Galvanic series
- Galvanization
- Gamma rays
- Gamma-ray astronomy
- Gangue
- Ganister
- Garnet
- Gas blending
- Gas centrifuges
- Gas chromatography
- Gas constant
- Gas detectors
- Gas mantles
- Gas metal arc welding
- Gas thermometer
- Gas turbines
- Gas-cooled fast reactor
- Gas-cooled reactor
- Gaseous diffusion
- Gaskets
- Gasoline
- Gastric acid
- Gastric lavage
- Gastric mucosa
- Gastroenteritis
- Gastrointestinal bleeding
- Gastrointestinal tract
- Gate dielectric
- Gate valves
- Gauge
- Gauge theory
- Gaussian curvature
- GeForce
- Gear
- Gear pumps
- Gelatin
- Gelcoat
- Gels
- Gemstones
- Gene expression
- General aviation
- General contractor
- Generation III reactors
- Generation IV reactors
- Genital herpes
- Geobacter sulfurreducens
- Geochemistry
- Geodesy
- Geodynamics
- Geography
- Geogrids
- Geology
- Geomembranes
- Geometrical frustration
- Geometrical optics
- Geophysics
- Geopolymer
- Geopolymer cement
- Geostationary orbit
- Geosynchronous orbit
- Geosynthetic clay liner
- Geosynthetics
- Geotechnical engineering
- Geotextiles
- Geothermal heating
- Geothermal power
- Germane
- Germanium
- Germanium dioxide
- Germicidal lamp
- Getter
- Geysers
- Giardiasis
- Gibbs free energy
- Gibbs isotherm
- Gibbs-Donnan effect
- Gibbs-Thomson equation
- Gibbsite
- Gigabit ethernet
- Gilchrist-Thomas process
- Gingivitis
- Girders
- Glacial period
- Glaciology
- Glass
- Glass cloth
- Glass electrode
- Glass fiber
- Glass melting furnace
- Glass production
- Glass recycling
- Glass transition
- Glass wool
- Glass-ceramic
- Glasses
- Glauconite
- Glazing
- Glider
- Global illumination
- Global warming potential
- Globalization
- Globally Harmonized System of Classification and Labelling of Chemicals
- Glomerulus
- Glovebox
- Glucose
- Glutamic acid
- Glutaraldehyde
- Glycerol
- Glycidol
- Glycol ethers
- Glycosides
- Glycosidic bonds