A symbol is an abbreviation of an element's name, which represents an atom of the element. Each element has its unique symbol.
Symbols are mostly the first alphabet of the element's name. For example: ‘’ is the symbol for oxygen, '' is the symbol for nitrogen, etc.
When the first alphabet of two or more elements is the same, then more than one alphabet is used and the first letter is always in uppercase and the second letter is in lowercase. For example: ‘’ for calcium and ‘’ for chlorine.
In some cases, abbreviations of Latin names are used. For example, the Latin name of sodium is Natrium, so its symbol is ''.