An action or statement in response to a stimulus or other event. / (chemistry) A transformation in which one or more substances is converted into another by combination or decomposition.

(politics) Favoring a return to an alleged golden age of the past; anti-progressive. / (chemistry) Of, pertaining to, participating in or inducing a chemical reaction. / In reaction to, as a result of.

(politics) One who is opposed to change and wants to reverse it, wishing for a return to an alleged golden age of the past.

(organic chemistry) The condensation reaction of an amino acid and a reducing sugar, followed by polymerization to form brown pigments - melanoidins; one of the causes of browning during cooking.

(chemistry) any reaction, typically involving organic compounds, in which a cyclic transition state is involved

(pharmacy, medicine) A reaction to a medication that is unusual and unpredictable, specific to a particular person. Unlike allergy, it can occur on first exposure to the medication; unlike a side effect, it affects only very few individuals.

(chemistry) a reaction in which radicals are added to both sides of a double or triple bond

(chemistry) a reaction in which a single electron is transferred from one molecule to another; one being oxidized and the other reduced (also known as a redox reaction); long-range electron transfer reactions are important in biological reactions involving metalloproteins such as haemoglobin

(organic chemistry) The trans oxidation of an alkene, to form a dihydric alcohol, catalyzed by iodine and silver benzoate.

(organic chemistry) The cycloaddition reaction between a conjugated diene and an alkene to form a cyclohexene ring.