Controlled removal of a material by a chemical, plasma or physical process. etch selectivity compares removal rates for different materials; directionality compares removal rates along different geometric directions. High selectivity does not imply a vertical profile, and high directionality does not guarantee an undamaged surface.

An electrostatic energy analyser using trajectories between two concentric hemispheres. electrons near a selected pass energy reach the exit aperture; entrance optics can retard faster electrons before analysis.

photoelectron spectroscopy using ultraviolet photons to probe occupied electronic states, often valence states. Empty states above the Fermi level require a different measurement or deliberate population.

A difference in the binding energy of the same core level for surface and bulk atoms of one material. Reduced coordination changes bonding and local potential; the relaxation that screens the photoemission core hole also changes. A measured shift combines these initial- and final-state effects and cannot by itself be converted into a unique local charge.

A core-binding-energy difference associated with chemical environment, such as bonding to an adsorbate or a change of oxidation state. Comparisons require the same core-level branch and a common calibrated energy reference. Local electrostatics, hybridization and final-state core-hole screening can all contribute.

The first-order rate coefficient for a specified photodissociation channel. It integrates spectral actinic flux, absorption cross section and channel quantum yield. Absorption without dissociation does not contribute to that channel's rate. Its units are inverse time.

The number of specified photochemical events per absorbed photon. A wavelength-dependent channel yield must be included when converting absorption into a chemical rate.

A regulatory subunit associated with a class I phosphoinositide 3-kinase complex. A band of its approximate mass does not establish its identity or whether a detected phosphorylation is activating.

A family of calcium-containing phosphate compounds. precipitation of such minerals can replicate soft tissues during phosphatization.

The cyclic anion ${\mathrm{P}}_3{\mathrm{O}}_9^{3-}$ comprising three tetrahedral $\mathrm{P}{\mathrm{O}}_4$ groups linked by three P–O–P bridges. Each phosphorus has two terminal oxygen atoms. It can bind a metal through one terminal oxygen from each phosphorus.

The view that living systems are physically realized and do not require a separate nonphysical substance. This does not by itself settle which level of description provides the best scientific explanation.

The capacity of a field to frame and test useful explanations at its own level of description, consistently with the physical realization of its objects.

A higher-level relationship or function can be implemented by different underlying physical mechanisms.

A role of a biological feature, interpreted either through its contribution to a current system or through its evolutionary history. A claim about function does not imply foresight in evolution.

A distinguishable measurable characteristic of an organism. Trait definitions matter: several correlated measurements need not represent independent dimensions of a phenotype.

Dependence of the phenotype expressed by a genotype on the environment. An immediate response can be beneficial or harmful; evolutionary change additionally requires a change in inherited properties across generations.

A blue, redox-active phenazine produced by Pseudomonas aeruginosa. Its biological effects depend on redox conditions, concentration and local electron acceptors.

A gill-bearing pharyngeal arch and its associated tissues.

A small-molecule inhibitor of ERK used experimentally to test pathway requirements. Developmental interpretation requires stage, dose, target-engagement and viability controls.