- Prepolymer
- Preservatives
- Pressure grouting
- Pressure head
- Pressure measurement
- Pressure solution
- Pressure swing adsorption
- Pressure-sensitive adhesive
- Pressure-sensitive tape
- Prestressed concrete
- Preterm birth
- Primary energy
- Primary standard
- Primers
- Printed electronics
- Prisms
- Probabilistic design
- Probability amplitude
- Process heat
- Proctor compaction test
- Prodrugs
- Product certification
- Product lifecycle
- Product lifetime
- Productivity
- Profilometer
- Progressing cavity pumps
- Progressive collapse
- Progressive stamping
- Projectiles
- Prokaryotes
- Prompt neutrons
- Propellants
- Propeller
- Propfan
- Propionic acid
- Proprietary software
- Propulsion
- Propylene
- Propylene glycol
- Prostaglandins
- Prostate
- Prostate cancer
- Prostheses
- Prosthetic groups
- Protecting groups
- Protein
- Protein biosynthesis
- Protein crystallization
- Protein folding
- Protein structure
- Protic solvents
- Proton-pump inhibitors
- Protonation
- Protoporphyrin IX
- Prototype
- Proxy
- Pseudomonas aeruginosa
- Pseudomorphs
- Psychiatry
- Psychrometric
- Public transport
- Puddling
- Pugmill
- Pulleys
- Pulmonary artery
- Pulp
- Pulsars
- Pultrusion
- Pulverizer
- Pumice
- Pump
- Pumped-storage hydroelectricity
- Punch
- Punching
- Pure bending
- Pure shear
- Pure tone
- Purified water
- Putrescine
- Pyramids
- Pyridine
- Pyridinium
- Pyridinium chlorochromate
- Pyrite
- Pyroclastic rock
- Pyroelectricity
- Pyrolysis
- Pyrolytic carbon
- Pyrometallurgy
- Pyrometers
- Pyrometric cones
- Pyrophyllite
- Pyroprocessing
- Pyrotechnic
- Pyrrole
- Pyruvic acid
- QCM
- Qanats
- Quadcopters
- Quadratic equations
- Quadratic functions
- Quadrilateral
- Quadruple bonds
- Quadrupole
- Quality assurance
- Quantification
- Quantum dots
- Quantum electrodynamics
- Quantum mechanics
- Quantum simulator
- Quantum statistical mechanics
- Quantum superposition
- Quantum technology
- Quantum tunnelling
- Quarry
- Quarry tile
- Quartic equation
- Quartz
- Quartz fiber
- Quartz inversion
- Quartzite
- Quasicrystals
- Quaternary ammonium cation
- Quenching
- Quick clay
- Quicksand
- R-value
- RAM
- RBMK
- RCC
- RCS
- RDI
- REL
- RHA
- RMS
- RNA
- RNS
- ROS
- RPM
- RTM
- RVP
- Racemic mixtures
- Rack and pinion
- Rack railway
- Rack unit
- Radial distribution function
- Radians
- Radiant flux
- Radiation hardening