Comma long sentences for clarity; however, this usage is regarded as an error in modern times. The comma and the quotation mark pairing can be used in several ways. In American English, the comma is commonly included inside a quotation mark: In Great Britain and many other parts of the world, punctuation is usually placed within quotation marks only if it is part of what is being quoted or referred to: There is also some difference regarding the use of the serial comma, which is an optional comma placed before the coordinating conjunction in a list of three or more items:
That that is is that that is not is not is that it it is That that is is that that is not is not is that it it is That that is is that that is not is not is that it it is is an English word sequence demonstrating syntactic ambiguity. It is used as an example illustrating the importance of proper punctuation. The sequence can be understood as any of four grammatically-correct sequences, each with at least four discrete sentences, by adding punctuation: The first two relate a simple philosophical proverb in the style of Parmenides that all that is, is, and that anything that does not exist does not. The phrase