(chemistry) Either the oxidation or the reduction component of a redox reaction

A process such as the fission of an atomic nucleus, or the fusion of one or more atomic nuclei and/or subatomic particles in which the number of protons and/or neutrons in a nucleus changes; the reaction products may contain a different element or a different isotope of the same element.

(chemistry) The reaction of a Grignard reagent (an organo-magnesium halide) with aldehydes or ketones to form secondary or tertiary alcohols

(chemistry) any of the participants present at the start of a chemical reaction

(physics, electrics) The opposition to the change in flow of current in an alternating current circuit, due to inductance and capacitance; the imaginary part of the impedance. Symbol: X.

An automatic safety feature of nuclear reactors where the control rods are automatically dropped into the reactor core when any of several emergency conditions are reached.

(molecular biology) A technique in molecular biology for creating multiple copies of DNA from a sample; used in genetic fingerprinting etc.

(idiomatic) An instantaneous reaction made without thought.

(chemistry) a reaction in which one functional group is replaced with another

(chemistry) a bimolecular nucleophilic substitution reaction