Is ‘Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo.’
a grammatically correct sentence?

You’ll be amazed to know that ‘Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo.’ is a grammatically correct sentence in American English. It is used as an example of how homonyms and homophones can be used in sentence to make perfect and complicated linguistic constructs.

In Linguistics (the scientific study of language), Homonym is a word that has two or more distinct meanings but same spelling & pronunciation and Homophones are words which are pronounced the same as another word but differs in meaning. This idea has been discussed in literature, in various forms, since 1967 where it appeared in Dmitri Borgmann's Beyond Language: Adventures in Word and Thought.

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

1. The city of Buffalo in New York, USA.

2. The animal “buffalo” in the plural (equivalent to “buffaloes”), only in order to avoid articles.

3. The verb “buffalo” meaning to ‘confuse, bully, deceive or intimidate’.

Substituting the synonym ‘bison’ for “buffalo” (the animal), ‘bully’ for “buffalo” (the verb) and leaving “Buffalo” to mean the city of Buffalo, New York, will yield:

“Buffalo bison, whom other Buffalo bison bully, themselves bully Buffalo bison.”