What punctuation mark is also known as a 'full stop'?

The punctuation mark also known as a “full stop” is a period.

The mark is a small dot placed on the baseline: “.” In Commonwealth English, “full stop” is the usual name, while “period” is especially common in North American English. It most often ends a declarative sentence, distinguishing a statement from a question or an exclamation.

Its history reaches back to ancient Greek punctuation. Aristophanes of Byzantium, working in Alexandria in the 3rd century BCE, used dots at different heights to signal pauses and divisions in thought. Over centuries, the low dot became the standard form used in European printing.

A period has other jobs too. It can appear in abbreviations, decimal numbers, website addresses and computer file names. It is not interchangeable with every nearby mark: a semicolon links related independent clauses, a comma marks a smaller separation, and an exclamation mark signals strong feeling or emphasis. In British English, the phrase “full stop” can also mean that a statement is final and not open to discussion.