Peer-reviewed journals almost always have a restriction against double
publication - submitting for publication a manuscript that is substantially the same as one that has already been published by another peer-reviewed journal. A related concept (which is also prohibited) is double submission, where the same or substantially the same manuscript is under consideration for publication by two peer-reviewed journals simultaneously. At the Journal of Micro/Nanolithography, MEMS, and MOEMS (JM3), for example, manuscript submission includes a requirement that the submitter acknowledge any prior publication of any of the major results/data/figures/etc. found in the submitted manuscript. But while submitting a manuscript that has already been published is an obvious problem, defining when duplicate content crosses the line to duplicate publication is not always easy. What, exactly, does “substantially the same” mean?