The symptoms of hay fever include: 1  frequent sneezing. 2  runny or blocked nose. 3  itchy, red or watery eyes (allergic conjunctivitis)  an itchy throat, mouth, nose and 1  ears. cough, caused by postnasal drip (mucus dripping down the throat from the back of the nose)
Definition. noun, plural: chemical reactions. A process in which one or more substances (reactants) are chemically changed into one or more new substances (products).Chemical changes may involve motion of electrons in the forming and breaking of chemical bonds.Supplement. process in which one or more substances (reactants) are chemically changed into one or more new substances (products). Chemical changes may involve motion of electrons in the forming and breaking of chemical bonds. Supplement.
2 chemical. noun. : any substance (as an acid) that is formed when two or more other substances act upon one another or that is used to produce a change in another substance.Spanish Central: Spanish translation of chemical. chemical. noun. : any substance (as an acid) that is formed when two or more other substances act upon one another or that is used to produce a change in another substance.