Academics have specialist search tools to check for plagarism, but us normal folks just plug a few words onto a good web search engine and see if any hits are registered.
Companies that sell essays to cheating students do usually publish a small sample of the essay as a 'taster' for customers but the bulk of it is not available to search engines, so you'll not find hits in that manner.
You can use plagiarism detection software, such as Turnitin or Grammarly, to check for plagiarism in a paper. These tools compare the text of the paper against a database of academic and online sources to identify any instances of copied content. Additionally, you can manually check for plagiarism by looking for inconsistencies in writing style, referencing, and originality of ideas.
One of the ways that most teachers tell that a paper has been copied is that it sounds much more educated than the student who turned it in! Professional writing always sounds better than amateur writing, and most students are amateur writers.
Another way you can tell if if you recognize the piece because you read it before somewhere.
You can sometimes detect if the answer is out of character. It is not written in the pattern the person speaks. You would need to know the person fairly well. Or you can use any program that does check for it.
You can easily check by copy pasting a paragraph in your browser to see if you get any matches (that are too close)
Adina's Deck The Case of the Plagiarized Paper - 2008 was released on: USA: 31 October 2008 (limited)
Pretty much every author of any significance has been plagiarized at some point.
The Universe.
Shakespeare.
Many authors have been.
To see if your paper has been plagiarized, visit www.duplichecker.com. After entering your text, the program will check each sentence against indexed website pages.
Stephenie Meyer
The only reason that this sentence is not incomprehensible is because it has been plagiarized.
I would suggest asking the teacher to provide evidence.
People plagiarize when they take written things from you and claim they wrote them.
The teacher cried "foul" on discovering this sentence had been plagiarized.
Just about any textbook writer.