These example sentences are selected automatically from various online news sources to reflect current usage of the word 'arachnophobia.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
Heavy water (deuterium oxide (2H 2O) or D 2O) is a form of water that contains a larger than normal amount of the hydrogen isotope deuterium (2H or D, also known as heavy hydrogen), rather than the common hydrogen-1 isotope (1H or H, also called protium) that makes up most of the hydrogen in regular water.
The chemical formula is: H2O. One important thing to note is that hydrogen with atomic mass 1 is the most abundant isotope of hydrogen but deuterium (D), a hydrogen isotope with atomic mass 2, is also found in nature so D2O is the chemical formula of heavy water as it is known chemically.