A neutralization reaction occurs when acids and bases in contact with each other. This phenomenon is also known as a double displacement or salt metathesis reaction. In this kind of reaction, parts are exchanged between each compound to produce new species. As a very common example, hydrochloric acid (HCl) and lye (sodium hydroxide or NaOH) – both very harmful substances – combine into table salt (sodium chloride or NaCl) and water (dihydrogen monoxide or H2O).