“Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo.” is a grammatically correct sentence used as an example of how homonyms and homophones can be used to construct complicated constructs.

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The sentence is unpunctuated and uses three different readings of the word “buffalo”. In order of their first use, these are:

• c. The city of Buffalo, New York (or any other place named “Buffalo”), which is used as an adjective in the sentence and is followed by the animal;
• a. The animal buffalo, in the plural (equivalent to “buffaloes”), in order to avoid articles (a noun);
• v. The verb “buffalo” meaning to bully, confuse, deceive, or intimidate.

Thus, the sentence when parsed reads as a description of the pecking order in the social hierarchy of buffaloes living in Buffalo:

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Bison from Buffalo, New York who are intimidated by other bison in their community also happen to intimidate other bison in their community.

From Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo. More good ones at List of linguistic example sentences.