- Phase separation
- Phase transitions
- Phase-change material
- Phase-field models
- Phase-transfer catalyst
- Phased array
- Phenocrysts
- Phenol
- Phenol formaldehyde resin
- Phenol red
- Phenolphthalein
- Phenols
- Phenylenediamine
- Phlegm
- Phonons
- Phosphate
- Phosphate binders
- Phosphate conversion coating
- Phosphate glass
- Phosphine
- Phosphodiester bonds
- Phosphogypsum
- Phospholipids
- Phosphonium
- Phosphor bronze
- Phosphorescent
- Phosphoric acid
- Phosphorite
- Phosphors
- Phosphorus pentachloride
- Phosphorus pentoxide
- Phosphorus trichloride
- Phosphorylation
- Photoacoustic effect
- Photocatalysis
- Photoconductivity
- Photocopier
- Photocurrent
- Photodetectors
- Photodiodes
- Photodisintegration
- Photodissociation
- Photoelasticity
- Photoelectric effect
- Photoemission spectroscopy
- Photoionisation cross section
- Photokeratitis
- Photoluminescence
- Photonic integrated circuit
- Photons
- Photophosphorylation
- Photoresist
- Photorespiration
- Photosensitivity
- Photothermal effect
- Photovoltaic
- Photovoltaic effect
- Photovoltaic systems
- Phthalates
- Phthalic anhydride
- Phyllite
- Physical constants
- Physical metallurgy
- Physical quantity
- Physiology
- Physisorption
- Phytic acid
- Phytoalexins
- Pi bond
- Pickling
- Picosecond
- Pidgeon process
- Piecewise
- Piers
- Piezoelectric motor
- Piezoelectricity
- Pig iron
- Pilling-Bedworth ratio
- Pinch analysis
- Pine tar
- Pineal gland
- Pipe
- Pipe insulation
- Pipeline
- Pipette
- Piston
- Piston pumps
- Pitch
- Pitching moment
- Pitting corrosion
- Placer deposits
- Placer mining
- Plagioclase
- Plain bearings
- Planck constant
- Planck's relation
- Plane curves
- Plane stress
- Planetary surface
- Planimeter
- Plant pathology
- Plasma
- Plasma arc welding
- Plasma electrolytic oxidation
- Plasma oscillation
- Plasma polymerization
- Plasma torch
- Plaster
- Plastic bottles
- Plastic film
- Plastic lumber
- Plastic pollution
- Plastic recycling
- Plasticity
- Plasticizers
- Plate column
- Plate glass
- Plate tectonics
- Plate theory
- Platelets
- Platform screen doors
- Plating
- Platinum
- Platinum black
- Platinum chloride
- Platinum nanoparticles
- Platinum-iridium alloy
- Plough
- Plug-in hybrid
- Plumbing
- Plumbosolvency
- Plunger pump
- Pluto
- Plutonium
- Plywood
- Pneumatics
- Pneumoconiosis
- Pneumonia
- Pneumonitis
- Podocyte
- Poiseuille
- Poisson's ratio
- Polar aprotic solvents
- Polar coordinate system
- Polar orbit
- Polarizability
- Polarization
- Polarography
- Polaroid
- Polders