Definitions

First Author

This generally should be the person that did most of the physical and intellectual labor for the content of the written work. If it isn't, there should be a very good reason.

Lead Author

Typically the person who initiates and leads the production of the written work. This is usually one person and they are responsible for the official submission of the manuscript somewhere. This is most often the first author, but need not be.

Customs

In mechanical engineering,

• It is customary to list the person that made the primary contribution and did the majority of the physical and intellectual labor as the first author.
• If an immediate advisor/supervisor of a student, PhD candidate, or Postdoc is a co-author on the manuscript, they are customarily listed last. This is because promotion judgement committees look for professors' last author listing as a sign of leadership.
• It is unclear if there is any common way the intermediate authors are ordered.

Guidelines

• Your thesis or dissertation is a single author document. The purpose of this document is to demonstrate that you can create such a document by yourself with only guidance from your advisors and peers. In essence, you write every single sentence and produce every single figure and no one else would write any sentences.
• If your thesis or dissertation includes one or more papers that have co-authorship, then you have to explain clearly in the thesis or dissertation what your individual contributions are. The CRediT system is a helpful framework for doing so. In principle, you should only include papers you are first author on, unless there is some special circumstance. Co-authors must consent to you including the paper in your thesis or dissertation.
• The ICMJE recommends authorship be based on four criteria and we use these criteria as our foundation for assigning authorship (quoted here):
  1. Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; AND
  2. Drafting the work or reviewing it critically for important intellectual content; AND
  3. Final approval of the version to be published; AND
  4. Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
• When you lead a co-authored manuscript you should discuss with each person that may make or may have made substantial contributions to see if they desire to be a co-author. There is no hard definition of what "substantial contributions" universally means, so this boils down to an interpersonal negotiation where the lead author has the responsibility to make things fair to the best of their ability.
• Explicitly propose the author order and get all authors agreement on it. If there is disagreement, the lead author should facilitate an agreement.
• Once you have negotiated the list of authors, they all must then do points 2., 3., and 4. in the ICJME criteria list to be confirmed as authors.
• You should never submit a manuscript to any publishing venue without the consent of all authors and agreement on points 1-4. It is the lead author's responsibility to give enough time for points 1-4 to be worked out. If reasonable time and deadlines have been given, and co-authors do not meet 1-4, they should be moved to the acknowledgements section of the paper. This should likely never be done for a journal paper due to its importance, but for less consequential things, like an abstract, it may be fine.
• It is perfectly fine to do projects and write papers without the involvement of Jason. Please do that! He should not be co-author on papers where he didn't meet points 1-4 even if he obtained your funding or is simply your supervisor. Of course, he loves to be invited for topics he is interested in and has time to contribute.