Physical world and mathematics

Precious metal

A precious metal is a rare, naturally occurring metallic element of high economic value, resistant to corrosion; the class is usually taken to include gold, silver, and the six platinum-group metals.

Precipitable water

Precipitable water (PW, also precipitable water vapor, PWV) is the total water vapor in a vertical atmospheric column, expressed as the depth of liquid water if fully condensed.

Precipitation

Precipitation, also called atmospheric precipitation, is water in liquid or solid form, such as rain, snow, sleet, or hail, that falls from clouds and reaches the ground, driving the water cycle.

Precipitation, also called chemical precipitation, is the formation of a solid precipitate from solution when a substance exceeds its solubility, occurring when the ion product exceeds the solubility product.

Precipitation hardening

Precipitation hardening, also called age hardening, is a heat-treatment method that strengthens metal alloys when fine second-phase particles precipitate and obstruct dislocation motion, underlying most high-strength aluminum and nickel-based alloys.

Precipitation polymerization

Precipitation polymerization is a free-radical polymerization technique, introduced by Kai Li and Harald Stöver in 1993, in which growing chains precipitate as uniform, surfactant-free microspheres used in chromatography, molecular imprinting, and drug delivery.

Precipitation types

Precipitation types are the distinct forms falling water takes, such as rain, snow, sleet, freezing rain, graupel, and hail, determined by the atmosphere's vertical temperature profile.

Precise point positioning

Precise point positioning (PPP) is a GNSS technique that estimates centimeter-level positions at a single receiver using precise satellite orbit and clock corrections, without nearby reference stations.

Precision and recall

Precision and recall are two paired measures of the performance of a binary classifier or retrieval system, often combined into the F1 score and generally trading off against each other.

Precision measurement methods in particle physics

Precision measurement methods in particle physics are the analysis techniques by which collider experiments extract masses, cross sections, and electroweak parameters, treating systematic uncertainty separately from statistical uncertainty.

Precision Time Protocol

The Precision Time Protocol (PTP) is a network protocol defined by IEEE 1588 that synchronizes device clocks over packet networks to accuracies around 100 nanoseconds.

Precognition

Precognition, also called premonition, is the apparent awareness of a future event that could not be anticipated by any known process; laboratory effects are small, and replications have failed.

Preconditioner

A preconditioner is a matrix, or any linear operator, applied to a linear system to give it better spectral properties so iterative methods converge faster.

Predicate abstraction

Predicate abstraction is a formal verification technique that converts infinite-state programs into finite Boolean models over chosen predicates, underpinning software model checkers such as SLAM, Blast, and CPAchecker.

Predictable process

A predictable process is a stochastic process whose value is known just before each time: it is measurable with respect to information available strictly before that time.

Prediction interval

A prediction interval is a statistical interval estimate that brackets a single future observation with a stated probability, and is wider than a confidence interval.

Prediction of stochastic processes

Prediction of stochastic processes is the estimation of a random process's future values from its observed past under a mean-square-error criterion, initiated independently by Kolmogorov and Wiener.

Prediction-powered inference

Prediction-powered inference (PPI) is a statistical framework that combines machine-learning predictions on a large unlabeled dataset with a small gold-standard labeled set, yielding valid confidence intervals and p-values.

Predictive maintenance

Predictive maintenance (PdM) is a maintenance strategy that uses condition monitoring and data analysis to predict failures, so maintenance happens just in time rather than on a fixed schedule.

Predictive modelling

Predictive modeling, also called predictive models, applies statistical models or data-mining algorithms to data to predict new or future observations, unlike explanatory modeling, which targets causal relationships.

Predictor–corrector method

A predictor–corrector method is a numerical method for solving ordinary differential equations: an explicit formula predicts the next step, and a more accurate implicit formula corrects it.

Predissociation

Predissociation is the breakup of a molecule that absorbs light into a bound excited state and then dissociates by a radiationless transition, leaving diffuse bands in absorption spectra.

Predual and ultraweak topology of von Neumann algebras

The predual of a von Neumann algebra is the Banach space whose dual it is, unique up to isometric isomorphism; it determines the ultraweak topology and normal maps.

Preference elicitation

Preference elicitation is the set of methods for turning a person's choices and trade-offs into a formal preference representation, such as utility-function parameters or attribute weights.

Preferential attachment

Preferential attachment is a network growth rule where new links attach to already well-connected vertices, explaining the scale-free structure of citation networks and the web.

Preferential enrichment

Preferential enrichment (PE) is a symmetry-breaking enantiomeric resolution phenomenon, reported in 1998 by Rui Tamura's group, in which simple recrystallization of racemic mixed crystals enriches one enantiomer in the mother liquor.

Preferential flow

Preferential flow is the movement of water and solutes through a small fraction of the pore network, such as roots, burrows, and cracks, bypassing most of the soil matrix.

Preferential solvation

Preferential solvation is the enrichment or depletion of one component of a solvent mixture in the solvation shell around a solute, compared with its bulk concentration.

Preferred IUPAC name

A preferred IUPAC name, or PIN, is the single name chosen by IUPAC rules from among the valid names for a chemical structure, introduced in 2013.