Plagiarism in the electronic age

The word 'plagiarism' finds its origins in the Greek word for 'kidnapping' and refers to the practice of passing off someone's work or ideas as one's own. How do we know this? It is the definition found in the New Oxford Dictionary of English. But this, in turn, raises a basic problem with the first sentence in this article. If the writer fails to identify the source, is he or she guilty of plagiarism? Consider the actual dictionary entry, which reads as follows: plagiarism noun [mass noun] the practice of taking someone else's work or ideas and passing them off as one's own. DERIVATIVES plagiarist noun plagiaristic adjective - ORIGIN early 17th cent: from Latin plagiarius 'kidnapper' (from plagium 'a kidnapping', from Greek plagion) + -ism.