An Etymological Dictionary of Astronomy and Astrophysics
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Chemistry: A bimolecular chemical reaction that involves removal of an atom or ion from a molecule. For example, hydrogen abstraction from methane: CH₄ + Cl → CH₃ + HCl.

→ abstraction; → reaction.

A succession of → nuclear fissions when the neutrons released by previous fissions produce other nuclear fissions which themselves cause other reactions and the reactions goes on increasing exponentially.

→ chain; → reaction.

A → change or → transformation in which a → substance → decomposes, → combines with other → substances, or interchanges constituents with other substances.

→ chemical; → reaction.

A process in which the energy, composition, or structure of an atomic nucleus changes.

→ nuclear; → reaction.

A device in which a nuclear fission chain reaction is maintained and controlled for the production of nuclear energy or radioactive isotopes.

→ nuclear; → reactor.

Newton's third law of motion, which states that for every action there must be an equal and opposite reaction.

→ principle; → action; → reaction.

A → thermonuclear reaction in which two protons collide at very high velocities and combine to form a → deuterium. See also → proton-proton chain.

→ proton; → reaction.

A nuclear reaction that takes place at high densities and relatively low temperatures. Pycnonuclear reactions are almost temperature independent and occur even at zero temperature. These reactions are extremely slow at densities typical for normal stars but intensify with increasing density. For example, carbon burns into heavier elements at densities over 10¹⁰ g cm^-3.

Pycnonuclear, from pycno- a combining form meaning "dense, thick," from Gk. pyknos "dense, solid" + → nuclear; → reaction.

Vâžireš, → reaction; cagâl-hasteyi, from cagâl, → dense, + hasteyi, → nuclear.

1) To act in response to an agent, influence, or stimulus.
2) To act in a reverse direction or manner; to act in opposition, as against some force.
3) Chem.: To undergo a → chemical reaction.

→ re-; → act.

The opposition to the flow of alternating current caused by the inductance and capacitance in a circuit rather than by resistance.

From → react + -ance a suffix of nouns.

Vâžirâyi state noun of vâžirâ agent noun of vâžiridan→ react.

1) General: A person or thing that reacts.
2) A substance on the left side of a → chemical equation.

From → react + -ant.

1) General: Action in response to some influence, event, stimulus.
2) An equal and opposite force exerted by a body against a force acting upon it. → principle of action and reaction.
3) A → nuclear reaction; → chain reaction.
4) → chemical reaction.

Verbal noun of → react.

The speed with which a → chemical reaction takes place. In other words, the change in → concentration of a → substance divided by the → time interval during which the change is observed.

→ reaction; → rate.

Tending to react. Pertaining to or characterized by reaction.

From → react + -ive a suffix of adjectives expressing tendency, disposition, function, connection, etc.

Vâžirandé verbal adj. of vâžiridan→ react; vâžireši, adj. of vâžireš→ reaction.

1) General: The quality or condition of being reactive.
2) Physics: A measure of the deviation from the condition at which a → nuclear reactor is critical.
3) Chem.: The relative → capacity of an → atom, → molecule, or → redical to undergo a → chemical reaction with another atom, molecule, or → compound.

From → reactive + → -ity.

1) A device for introducing reactance into an electrical circuit (e.g. a capacitor).
2) Same as → nuclear reactor.

From → react + → -or.

The part of a → nuclear reactor in which → nuclear fission takes place and huge quantities of heat energy are generated.

→ reactor; → core.

A nuclear reactor designed for radionuclide production, materials testing, and training.

→ research; → reactor.

A nuclear reaction whose probability is enhanced at an energy corresponding to an energy level of one of the nuclei. → resonance capture.

Resonant, verbal adj. of → resonate; → reaction.

A → nuclear reactor in which the rate of production of → fission neutrons is lower than the rate of production in the previous generation, and therefore the number of fissions decreases over time.

→ subcritical; → reactor.