What is a one or two-letter abbreviation used to represent an element called?

A one or two-letter abbreviation used to represent an element is called a symbol. Each element in the periodic table is assigned a unique symbol that is derived from its name, often based on its Latin or Greek origin. For example, the symbol for hydrogen is 'H', while the symbol for oxygen is 'O'. These symbols allow chemists and scientists to quickly identify elements in chemical equations and formulas, making communication about chemical substances more efficient.

The other terms refer to different concepts: a formula represents a compound or molecule formed by combining elements in specific ratios, while a molecule refers to a group of atoms bonded together. A compound is a substance composed of two or more different elements that are chemically bonded. Understanding symbols is fundamental in chemistry, as they provide a shorthand method for identifying elements without needing to write out their full names.