Plagiarism is the act of knowingly or unknowingly copying intellectual property without crediting the creator for their work and passing their work off as one's own.
The simple answer to whether a plagiarism checker is necessary to write original English text is no. It is not necessary to use a plagiarism checker if the text is composed of unique content. If an author is performing original research, writing creatively, expressing opinions, and/or forming a hypothesis, it is unlikely that content will appear elsewhere. A simple search query from a major search engine will suffice as a plagiarism checker for most written text. Most search engines have character limits, so multiple searches will be required to check for lifted content using this method.
A small search query string passed through a search engine will result in a better plagiarism check. It is not effective to copy and paste the entire contents of a document, as it is unlikely that the entirety of the document will result in an exact match. Smaller search strings or queries are more likely to result in a match. An author worried about plagiarism should rewrite text that results in matches from this plagiarism checker.
Journal submissions should also be queried against academic search engines that specifically contain published journals. Scientific discovery is built upon previous studies of other researchers. It is okay to come to the same conclusion of a previous author, but the previously published author should be cited.
What is the difference between plagiarism and paraphrasing? Paraphrasing or rewriting text while maintaining the meaning of the text is technically not plagiarism. Paraphrasing is a gray area and should be avoided if the purpose of rearranging text is to pass another author's work as one's own. Paraphrasing is well suited for summarizing larger texts, like an abstract for a journal. A summary can give a reader a quick synopsis before they read the entire text.
"Success is walking from failure to failure with no loss of enthusiasm." –Winston Churchill
This quote from Winston Churchill is paraphrased below for the purpose of demonstration.
"Happily marching from one defeat to another is the definition of success."
Plagiarism differs from paraphrasing because plagiarized text is lifted verbatim and incorporated directly in the plagiarizing author's text. There is no attempt by the plagiarizing author to hide the theft of intellectual property.
Proof Reading, LLC does not own a plagiarism checker or use similar software. Our editors discover plagiarism when the text of a client's work changes dramatically and the flow of a sentence, paragraph, or chapter changes tense, tone, or point of view. Our editors take these suspicious sections and check for plagiarism using small sections of the client's text and pass them through a search query. This plagiarism checker method will catch most inadvertent plagiarism in our clients' submissions. Our editors will leave a comment using track changes to notify the client they must cite the borrowed text before the client submits their document to their academic institution or journal.