- Gneiss
- Goethite
- Gold
- Gold mining
- Gonads
- Goniometer
- Goodman relation
- Gore-Tex
- Gout
- Grade
- Grade separation
- Grading
- Graduated cylinder
- Grain
- Grain boundary
- Grain boundary strengthening
- Grain growth
- Grain size
- Grand potential
- Granite
- Granitoid
- Granodiorite
- Granophyre
- Granular materials
- Granularity
- Granulation
- Granules
- Granulite
- Granulocytes
- Graph of a function
- Graphene
- Graphics card
- Graphics pipeline
- Graphite
- Graphite intercalation compound
- Graphite-moderated reactors
- Gravel
- Gravimetric analysis
- Gravimetry
- Gravitational constant
- Gravitational waves
- Gravity
- Gravity of earth
- Gray iron
- Grease
- Grease trap
- Great Green Wall
- Green buildings
- Green hydrogen
- Green rust
- Greenhouse effect
- Greenhouse gas emissions
- Greenhouse gas inventory
- Greenhouse gases
- Greenschist
- Grey matter
- Greywacke
- Grignard reaction
- Grignard reagents
- Grinding
- Grinding wheels
- Grog
- Grooves
- Ground effect
- Ground glass joint
- Ground wave
- Groundwater
- Groundwater pollution
- Group-velocity dispersion
- Grout
- Growth medium
- Guard rails
- Gull wing
- Gunmetal
- Guns
- Guy-wires
- Gypsum
- Gypsum block
- Gypsum concrete
- Gyroscopes
- HAZ
- HDD
- HDPE pipe
- HF
- HIV
- HOPG
- HRSG
- HSAB theory
- HTR-10
- HTR-PM
- HVDC converter
- HVPE
- Haber process
- Haematopoiesis
- Hafnium
- Hafnium oxide
- Hail
- Hair loss
- Haldane effect
- Half-cells
- Half-life
- Halide
- Halite
- Hall effect
- Hall-effect thrusters
- Haloalkanes
- Halocarbons
- Halogen bond
- Halogenation
- Halogens
- Halomethanes
- Halotolerant
- Hamaker constant
- Hammer
- Hammer drill
- Hand drill
- Hand pumps
- Hand tools
- Handedness
- Handrails
- Handwriting recognition
- Hansen solubility parameter
- Haptic technology
- Hapticity
- Harbor
- Hard water
- Hardenability
- Hardening
- Hardness
- Hardware acceleration
- Harmful algal bloom
- Hazardous waste
- Head gasket
- Headaches
- Headphones
- Hearing aids
- Hearing loss
- Hearing protection devices
- Heart failure
- Heart rate
- Heartburn
- Heat capacity
- Heat capacity ratio
- Heat death of the universe
- Heat engine
- Heat equation
- Heat exchanger
- Heat flux
- Heat flux sensor
- Heat of combustion