Sean wrote a research paper last week but didnt cite any of his source l. What is this called

The act of taking someone else's work without giving credit to the rightful owner is known as Plagiarism.

If plagiarism is acted upon, you can be expelled from class (if in school) and possibly can be arrested. If a plagiarist makes up to $2,500 minimal from stolen material, they can face up to $250,000 in fines and up to 10 years in jail.