Why “authorship” is not one thing
A single research paper can carry several distinct kinds of authorship information at once: a formal authorship qualification test that every listed name has to pass, a byline position (first, last, corresponding) that signals something about each person’s role but isn’t itself a qualification, and — increasingly — a CRediT contribution statement that names the specific tasks each person actually did. On top of these legitimate categories sit two well-documented misattribution problems, ghost authorship and gift authorship, that editors and integrity offices treat as research-integrity violations, not stylistic choices.
This guide orients across all of it: the formal qualification test, the conventional positional roles, the CRediT alternative, and the illegitimate types — with links to CASRAI’s dedicated entries on each individual concept for full definitions, examples, and edge cases.
The baseline: who qualifies as an author at all
Before any position or role question matters, a contributor has to clear a qualification threshold. The most widely adopted version is the International Committee of Medical Journal Editors’ (ICMJE) four-part test, which requires all four of the following (an AND test, not an OR test):
- Substantial contribution to the conception or design of the work, or the acquisition, analysis, or interpretation of data;
- Drafting the work or revising it critically for important intellectual content;
- Final approval of the version to be published;
- Agreement to be accountable for all aspects of the work, including ensuring questions about its accuracy or integrity are appropriately investigated and resolved.
See CASRAI’s dedicated Authorship entry and the ICMJE Authorship Criteria guide for the full test and its limits — meeting some but not all four criteria qualifies a person for an acknowledgement, not a byline. Everything below this line describes how qualifying authors are then ordered, labelled, or (in the two illegitimate cases) added without qualifying at all.
Positional roles: what byline order conventionally signals
In fields that use a contribution-ranked byline — most consistently biomedicine, the life sciences, and much of the natural sciences — where a name sits in the author list carries an informal but widely understood meaning layered on top of the formal qualification test. None of these positions is itself an authorship criterion; they answer “where does this already-qualifying author’s contribution rank,” not “does this person qualify.”
First author
The name listed first. Conventionally understood to have carried out the largest share of the hands-on work — the bulk of the experiments or analysis and typically the first manuscript draft. See First Author for the full definition, including the important caveat that in fields using strictly alphabetical ordering (much of mathematics, economics, and parts of theoretical physics), first position carries no contribution ranking at all.
Last author / senior author
In the same contribution-ranked fields, the final position in the byline is conventionally read as the supervising principal investigator — the person who secured funding, oversaw the project, and takes overall responsibility for its integrity, without necessarily having done the hands-on experimental or analytical work. This last-author or senior-author reading is a discipline convention rather than a formally defined criterion, and — like first-author position — it does not apply in alphabetical-order fields.
Corresponding author
The individual (or individuals) designated to handle submission, respond to editors and reviewers, and serve as the point of contact after publication. Corresponding-author status is an administrative and communication role, not a seniority marker on its own — it is sometimes but not always held by the first or last author. See Corresponding Author for what ICMJE and journals actually require of the role.
Co-first and equal-contribution authorship
When two or more contributors did comparably substantial work, journals increasingly allow a co-first or equal-contribution designation — typically a footnote or symbol next to more than one name, stating that those authors “contributed equally.” This solves a real ordering problem (someone still has to be listed literally first) but the designation is systemically fragile: major indexing and citation systems routinely strip equal-contribution footnotes even when a journal’s own PDF states them clearly, which can distort downstream credit in metrics, CVs, and hiring or tenure review. See Co-First Authorship for the full picture, including how this differs from CRediT’s own “degree of contribution” qualifier (below).
Lead author (non-byline-order contexts)
Outside conventional first/last biomedical bylines, some structures use “lead author” as a distinct role label rather than a position. Large multi-author assessment processes — the IPCC’s assessment reports are a documented example — assign Lead Author and Coordinating Lead Author roles that coordinate a chapter’s writing and synthesis, in a structure with no single “first author” slot at all. The label is also used informally in some fields as a synonym for “first author” or “corresponding author”; check a specific journal’s or funder’s own usage rather than assuming one meaning.
Major contributor
Not a defined category in ICMJE, CRediT, or any research-integrity standard, but a useful functional description for a contribution broad and substantial enough that it typically meets — or is expected to meet — the authorship threshold, as distinct from a narrower “minor” contribution more appropriately handled through acknowledgement. See Major Contributor.
CRediT: the precise alternative to position-based roles
Positional roles (first/last/corresponding) are useful shorthand, but they compress a lot of different work into a small number of slots, and they don’t travel well across disciplines that don’t rank bylines by contribution at all. The Contributor Roles Taxonomy (CRediT) takes a different approach: instead of inferring what someone did from where their name sits, it names the specific tasks directly, using fourteen standardized role terms (Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, and Writing – review & editing), each of which can be assigned to one or more contributors, optionally with a degree-of-contribution qualifier (lead, equal, or supporting).
CRediT was first published in 2014 and is now a full American National Standard, ANSI/NISO Z39.104-2022 — CASRAI has stewarded the taxonomy since 2014 but did not originate it. A CRediT statement and formal authorship qualification answer related but different questions: a person can appear in a CRediT statement (credited for a role like Formal analysis or Resources) without meeting the full ICMJE authorship test, and CRediT itself does not decide who qualifies as an author — it describes what a already-qualifying author (or, in some journals’ usage, any credited contributor) actually did. See the CRediT & Authorship Attribution pillar for the complete framework, and CRediT vs. ICMJE for how the two systems relate.
Illegitimate authorship: ghost and gift authorship
Two authorship patterns are treated by journals, funders, and research-integrity offices as violations rather than legitimate variations, because both break the link between the byline and who actually did (or is accountable for) the work.
Ghost authorship
Ghost authorship is the undisclosed substantial contribution to a manuscript by a person not listed as an author or named in the acknowledgements. A contribution is ghost-written when, by ICMJE criteria, it would have warranted authorship had it been disclosed — the paradigm case is a professional or industry medical writer who drafts a clinical-trial manuscript that is then submitted solely under the names of the named academic investigators, with no acknowledgement of the writer’s role. Ghost authorship is not the same as disclosed, acknowledged medical-writing support (which is legitimate and routinely required to be stated). See Ghost authorship.
Gift (honorary/guest) authorship
Gift authorship is the inclusion, as an author, of a person who did not meet the substantive authorship criteria — typically added as a courtesy, in exchange for resources or access, or for the prestige their name lends the paper. The practical test: an authorship is a gift when removing the named person would require no change to the manuscript itself, because they contributed nothing that shows up in the text, data, or analysis. See Gift authorship.
Ghost and gift authorship are frequently discussed together because they are mirror-image failures of the same underlying rule: authorship is deliberately narrower than “did real work on this.” Doing qualifying work without being listed is ghost authorship; being listed without doing qualifying work is gift authorship. Both distort the scholarly record’s accountability chain — readers can no longer tell who is actually answerable for the work’s accuracy and integrity — which is why both are addressed explicitly in ICMJE’s recommendations and most journals’ authorship policies, and why authorship disagreements arising from either pattern are handled through a journal’s formal authorship dispute process rather than informally.
Other authorship-adjacent concepts
A few related terms round out the landscape:
- Co-authorship — the general condition of a work having more than one author, distinct from the specific co-first-author designation above.
- Pseudonymous and anonymous authorship — cases where a contributor’s identity is deliberately withheld or replaced with a pseudonym, governed by separate disclosure norms from ghost authorship (where the omission is undisclosed and typically not the contributor’s own choice).
- Authorship order disputes — disagreements between qualifying authors about byline order or role recognition are common enough to have established resolution processes; see the Resolving Authorship Order Disputes guide.
How the pieces fit together
In practice, a single paper typically carries all of these at once, layered rather than competing:
- Every named author has to independently clear the qualification threshold (ICMJE’s four criteria or an equivalent journal policy).
- Among qualifying authors, byline order conventionally signals relative contribution in contribution-ranked fields (first author, last/senior author), or nothing at all in alphabetical-order fields.
- One or more authors take on the administrative corresponding-author role, separate from seniority.
- Where a journal or funder requires it, a CRediT statement separately and precisely names what each contributor actually did, independent of where their name sits in the list.
- Anyone added to, or omitted from, that list in a way that breaks the link between the byline and actual qualifying work is a ghost- or gift-authorship problem, not a legitimate variant.
Understanding which of these five layers a given question is actually about — qualification, position, role, contribution detail, or misattribution — is usually enough to resolve confusion about “who should be an author” or “why is this person listed where they are.”
Frequently asked questions
Is first author always the person who did the most work?
Only as a convention in contribution-ranked fields (biomedicine, life sciences, much of the natural sciences), and even there it is an informal signal, not a rule enforced by any standard. In alphabetical-ordering fields such as much of economics and mathematics, first position carries no contribution ranking at all.
Can the same person be both first author and corresponding author?
Yes — the two roles are independent and frequently overlap, but neither requires the other. A senior/last author, a first author, or another team member can each serve as corresponding author depending on the group’s own arrangement.
Does a CRediT statement replace the need to decide byline order?
No. CRediT documents what each person did; it does not itself set byline order or decide who qualifies as an author. Journals that use CRediT still separately determine and publish the conventional author list and order.
Is gift authorship ever acceptable if the added person is senior or influential?
No. Seniority, funding control, or departmental courtesy are not authorship criteria under ICMJE or equivalent policies; adding a name for those reasons alone, without a qualifying contribution, is gift authorship regardless of the person’s status.
What’s the difference between ghost authorship and an acknowledged writer?
Disclosure. A medical writer or other substantial contributor who is named in the acknowledgements or methods section, with their role described, is not ghost-written — ghost authorship specifically requires that the contribution be undisclosed.
Related dedicated pages
For deeper treatment of individual positional roles referenced above, see:
- Last Author — what the last-author position signals and how it differs from corresponding authorship
- Senior Author vs. First Author — a direct comparison of what each position signals
- Lead Author — disambiguating this informal/ambiguous term
