The theft of ideas (such as the plots of narrative or dramatic works) or of written passages or works, where these are passed off as one's own work without acknowledgement of their true origin; or a piece of writing thus stolen. Plagiarism is not always easily separable from imitation, adaptation, or pastiche , but is usually distinguished by its dishonest intention.
"plagiarism" The Oxford Dictionary of Literary Terms. 2008. Oxford Reference Online. Oxford University Press (emphasis mine).
Will I be punished if I plagiarised accidental?
Every case is different and will be judged differently. However, pleading ignorance or claiming that the plagiarism is accidental will not be enough. It is always a good idea to include full citation details when taking notes to help avoid accidental plagiarism. Refer to the library's resources on citation and referencing for help.
What if I write something and find the same idea in a book?
That's too bad, they got there first! You will still have to cite the published source.
What is self-plagiarism? Why can’t I re-use my own work?
According to the American Psychological Association (2010), self-plagiarism refers to "the practice of presenting one’s own previously published work as though it were new” (pg. 170).
While it may sound oxymoronic to steal from yourself, you are committing self-plagiarism if you reuse your own work without proper citation. Refer to Dellavalle's (2009) article for more details on the topic of self-plagiarism.
Copyright is a set of rights provided by the U.S. Constitution "to promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective writing and Discoveries" (Article 1, Section 8 of the U.S. Constitution).
So what does this mean?
Copyright provides a set of rights to the authors of "original works", which can include literary, dramatic, musical, artistic, audiovisual, and other works like software. These rights are given to works regardless of publishing status, so published and unpublished works are granted these rights, upon creation. It does not, however, protect ideas; it protects the expression of ideas.
Copyright grants these exclusive rights:
to reproduce the work (i.e., to make copies)
to prepare derivative works (i.e., creating an adaptation, like making a movie from a book or translating a book from French to English)
to distribute copies publicly
to perform the work publicly
to display the work publicly
in the case of sound recording, to perform the work publicly as a digital audio transmission
Copyright can be transferred in part or all to another person or entity (like a publisher) with written consent.
Some exceptions do apply, like fair use. If a person uses copyrighted material, where exceptions do not apply and without permission from the author, the user could be held liable for copyright infringement. Read through the "Exceptions" tab to learn more about the exceptions to copyright.
Source: Butler University Libraries Libguides