Technology glossary

Peer-to-Peer Sinkhole

Defender-controlled infrastructure inserted into a peer-to-peer network so infected devices connect to a monitoring or containment system instead of receiving commands from the malicious operator.

Penumbra

The lighter, outer part of a shadow, where only part of a light source is blocked. Observers inside the Moon's penumbra during an eclipse see the Sun partly, not fully, covered.

Peptide Therapeutic

A medicine built from short chains of amino acids, often designed to bind a biological target with high specificity.

Perceptual Camouflage

A camouflage strategy designed to exploit how a person or machine-vision system perceives and interprets sensory information. Rather than making an object physically invisible, it alters cues such as shape, contrast, motion, texture, or recognizable patterns to reduce detection or identification.

Peripheral Lung Nodule

A small rounded abnormality located near the outer regions of the lung, often detected on CT imaging and sometimes requiring biopsy to determine its cause.

Permafrost Carbon Feedback

The extra warming caused when thawing permanently frozen ground allows microbes to decompose stored organic matter and release carbon dioxide or methane, which can drive further thaw.

Permanently Shadowed Region(PSR)

An area near a planetary body's pole where sunlight never reaches the surface because of local terrain and the low solar angle. On the Moon, these cold traps may preserve water ice and other volatile materials for very long periods.

Permission Authority

A security component that makes the final decision on whether a requested action may proceed, be denied or require human approval.

Perovskite Laser Cell

A photovoltaic device made with a perovskite semiconductor and optimized to convert light from a specific laser wavelength into electricity. Unlike an ordinary solar cell, it is designed for a narrow and controlled light source rather than the broad spectrum of sunlight.

Perovskite-Silicon Tandem Solar Cell

A photovoltaic device that stacks a perovskite absorber over a silicon solar cell so each layer captures a different portion of the sunlight spectrum. This tandem design can exceed the efficiency limit of a conventional single-junction silicon cell, though durability and scalable manufacturing remain challenges.

Persistence

In cybersecurity, persistence refers to techniques used to maintain access to a compromised system across time, restarts, credential changes, or defensive actions.

Persistent Contrail

An aircraft condensation trail that remains long enough to spread into cirrus-like cloud. It forms when ice crystals survive in cold, humid upper air and can produce a net warming effect by trapping outgoing heat.

Personalized Cancer Vaccine

A therapeutic vaccine designed from molecular features of an individual patient's tumor, often its unique mutations or neoantigens, to stimulate a targeted immune response. It is intended to treat or reduce recurrence of existing cancer, not to prevent cancer in the same way as routine infectious-disease vaccines.

PFAS (Per- and Polyfluoroalkyl Substances)

A family of nearly 5,000 synthetic chemicals used since the 1940s in nonstick cookware, waterproof fabric, and firefighting foam. Known as "forever chemicals" because their strong carbon-fluorine bonds resist breaking down, PFAS now turn up in the blood of most people tested worldwide and are suspected of contributing to metabolic and immune problems.

pH Swing

A controlled shift between acidic and alkaline conditions used to change which chemical form a dissolved substance takes, enabling processes such as carbon dioxide release and reagent regeneration.

PHA (Polyhydroxyalkanoate)

A carbon-storage compound many bacteria and archaea produce naturally inside their cells as an energy reserve, and which is also manufactured industrially as a biodegradable alternative to conventional plastic.

Phagocytosis

The process by which a cell surrounds and digests particles, microbes or other cells.

Phase III Trial

A late-stage clinical trial that evaluates an intervention in a relatively large participant population, often comparing it with standard care or a control. It is designed to confirm efficacy, characterize common adverse effects, and provide evidence for regulatory decisions.

Phonon

A quantum of collective vibration in a crystal lattice that can carry heat and sound.

Photoisomerization

A reversible change in a molecule's structure triggered by absorbing light. The two molecular forms can differ in color, polarity, reactivity or how they interact with a surrounding material.

Phylogenetic Comparative Method

A family of statistical methods that compares traits across related species while accounting for their shared evolutionary history.

Physical Reservoir Computing

A computing approach that uses the natural dynamics of a physical system to transform time-varying data for machine-learning tasks.

Planetary Contraction

The gradual reduction in a planet's size as its interior loses heat and contracts. The shrinking interior places compressive stress on the outer rocky shell, which can create thrust faults, cliffs and ridges that preserve a record of thermal evolution.

Planetesimal

A relatively small solid body formed in a young planetary system. Planetesimals can collide and combine into planets, remain as asteroids or comets, or be broken apart and absorbed by their star.

Plant Immune Receptor

A plant protein that recognizes signs of a pathogen and activates immune defenses.

Platform Liability

The legal responsibility an online platform may bear for content, transactions, products, conduct, or harms connected to its service. The scope differs by jurisdiction and often depends on the platform's knowledge, role, moderation practices, and compliance with notice or due-diligence duties.

Plug-In Hybrid Electric Vehicle(PHEV)

A vehicle with both an internal-combustion engine and an electric motor powered by a battery that can be charged from an external source. It can travel a limited distance on electricity before using the engine, with actual fuel savings depending heavily on charging and driving patterns.

Pneumatic Actuation

The production of mechanical movement using compressed air or another gas. Pressure is directed into cylinders, chambers, or flexible structures to create force and motion, a method common in industrial equipment and soft robotics.

Pneumothorax

A condition in which air collects between the lung and chest wall, potentially causing part or all of the lung to collapse.

PNT Resilience

PNT resilience is the ability to maintain or recover reliable positioning, navigation and timing when a primary source such as GNSS is disrupted, degraded or manipulated. It can involve redundant signals, local clocks, inertial sensors and alternative timing sources.