There is an English word that can be used up to four times in a row without modifying the spelling and form a valid grammatical sentence.
Do you know what word is that?
The word is "Buffalo".
According to the dictionary meaning, Buffalo is a noun meaning an animal. It is also a verb meaning "to bully".
Sentence: Buffalo.
Meaning: Go and bully someone.
Sentence: Buffalo buffalo.
Meaning: Animals bully.
Sentence: Buffalo buffalo buffalo.
Meaning: Animals bully other animals.
Sentence: Buffalo buffalo buffalo buffalo.
Meaning: Animals that are bullied by other animals, in turn, bully other animals.