Article processing charges (APC)

Article processing charges (APC) are publication fees that are charged when a journal article is accepted for publication in an open access journal or a hybrid journal. They are usually paid by the employing institution or by research funding institutions on behalf of the authors. Other terms are: article fee, article charges, processing charges, page charges, publication charges.


Book processing charges (BPC)

Book processing charges (BPC) are publication fees that are charged when publishing an open access book (monograph or edited volume). They are usually paid by the employing institution or by research funding institutions on behalf of the authors. Other terms are: book charges, processing charges, publication charges.


Closed access

Closed access refers to restricted, non-free access to scientific literature. In this case, access is usually only possible exclusively after payment, which is why it is also referred to as a paywall. The opposite of closed access is open access.

Corresponding author

A corresponding author is the main contact person for a publication, usually a journal article, in dealings with the publisher and the audience. Sometimes it is not explicitly indicated who is the corresponding author, the first named author assumes this capacity. Publication fees are usually defrayed by first or corresponding authors.

Creative Commons licences

Creative Commons licenses (CC licenses) are standard licensing agreements that allow content creators or authors to easily grant the public rights of use to their works, resulting in the creation of free content. On a separate page, we provide further information on licences for open access, including Creative Commons licences.


Double dipping

Double dipping is a term used to criticize the business model of hybrid journals, in which the budgets of libraries and publishing institutions are double-burdened by charging fees for journal access (through so-called subscriptions) and also by charging publication fees for open access articles appearing in the journal (so-called article processing charges).

Digital object identifier (DOI)

A digital object identifier (DOI) is a persistent identifier for digital resources. By means of an identification number in the format 10.<prefix>/<ID>, a unique and permanent link to a digital resource is provided. The basic principle is that a resource can thus always be found, even if the actual target of this resource (usually a web address) changes. The DOI system is the best known internationally and is most widely used for scientific articles and other scientific publications (including data). The repository of the Humboldt-Universität, the so-called edoc-Server (more information), also makes use of the DOI system (example of a link to a publication by means of a DOI: 10.18452/20562). A comparable technical solution is the URN system.


Free access

Free access generally refers to access to a work free of charge, but without any further rights of use, which means that the work can only be used within the scope of the legally permitted uses. In particular, reuse of the work (for example, the creation and publication of adapted and modified versions) is not possible in this case, whereas reuse is usually allowed in the case of open access.


Gold open access

Gold open access refers to the immediate and free access to a work published for the first time (at its original place of publication). This can be, for example, a scientific journal article or essay in a volume, a monograph, an edited volume, a conference proceedings or a research report. Another route of open access is green open access. Our Quick Guide provides more information.

Green open access

Green open access refers to the release of a version of an already published but not yet freely accessible work. In most cases, manuscript versions of such a publication are made freely accessible in this way (see preprint and postprint), but it can also be the actual published version. Here, the publication is usually made available via so-called repositories. Green open access can be achieved through so-called self-archiving and through the exercise of the secondary publication right. Green open access is therefore primarily relevant for publications in scientific journals. Another route of open access is gold open access. Our Quick Guide provides more information.


Hybrid open access

Hybrid open access refers to the implementation model of open access in so-called hybrid journals. Hybrid open access is not an additional or alternative route to gold open access and green open access, but rather used for this particular way of implementing gold open access. Hybrid open access is often used as more of a marketing term.

Hybrid journal

A hybrid journal is a subscription-based journal in which individual articles are made freely available (i.e., open access) in return for payment of so-called article processing charges. This model is also referred to as hybrid open access. This option of open access publishing is advertised by publishers with terms such as 'Author's Choice', 'Online Open', or 'Open Choice', among others.


Initial publication

An initial publication (German: Erstveröffentlichung) is the first-time publication of a scientific work at its original place of publication. This usually refers to the publication of the scientific work (usually an article or book) by a publisher, the last step of a publication process. It can also refer to a scientific work published not by a traditional publisher but another institution (for example, a research report). An initial publication may not be freely accessible (see closed access) or freely accessible (see open access); in the latter case, this corresponds to gold open access.


Open access

Open access refers to the free access to scientific results. This way, scientific publications are digital, free of charge and publicly accessible via the internet. Open access publications can generally be read, copied, distributed, printed, searched and otherwise reused without technical or legal barriers. Open access is thus the opposite of closed access, the restricted access customary in scientific publishing (mostly realized through the subscription model), which is usually only possible exclusively after payment, also known as a paywall. Our Quick Guide provides an introductory overview of open access.

Open access journal

An open access journal is a journal in which all articles appear via gold open access, so that all articles appearing in the journal are immediately digitally and freely accessible at the original place of publication. Just like non-open-access scholarly journals, open access journals are compatible with review processes such as peer review and may additionally be published in print.


ORCID is a non-profit initiative that provides scientists with a unique identifier, called ORCID iD, and a mechanism to link their identifier to their research results and activities. The ORCID iD is an alphanumeric 16-digit code (example: 0000-0002-1825-0097) that does not change when the name of the author changes or when the author changes institutions. It therefore addresses the difficulty to clearly identify authors when their names change or if names are identical. We provide further information on author identification on a separate page.



A paywall refers to access to a resource that is restricted by required payment (see also closed access). In the scientific publication system, it is mostly scientific articles and books that are only accessible after payment.

Persistent identifier

A persistent identifier (PID) is used to uniquely and permanently reference a digital resource (for example, research data) by assigning a number that can be uniquely referenced. The basic principle is that a resource with a persistent identifier can always be found, even if the actual target of this resource (usually a web address) changes. This prevents the phenomenon of resources no longer available under a specific web address (known as link rot). In science, the DOI system is most widely used, also common is the URN system. The website on research data management at Humboldt-Universität provides more information on persistent identification.


A postprint is the version of a scientific publication that has gone through a review process (in contrast to a preprint), usually peer review, and has been accepted for publication, but has not yet been typeset, formatted, and designed (see published version). For journal articles, the postprint is the accepted manuscript version of the article. Postprints play an important role for green open access.

Predatory publishing

Predatory publishing refers to business practices that offer publishing services in return for publication fees, mostly under the pretext of open access, but do not perform these services at all or only inadequately. This means, for example, that no quality assurance process (such as peer review) is carried out or that no editorial work is carried out, which would be expected in terms of ensuring scientific standards and quality. Publishers who engage in predatory publishing are also referred to as predatory publishers, and their journals as predatory journals. We provide more information about predatory publishing and how you can recognize it on a dedicated page.


A preprint is the version of a scientific publication that has not yet undergone a review process (in contrast to the postprint and the final published version), usually peer review. For journal articles, the preprint is the submitted manuscript version of the article. Preprints play an important role for green open access. In some disciplines, preprint servers are widely used to deposit preprints.

Preprint server

Preprint servers are used to store preprints and are widely used in certain disciplines (especially in the natural sciences, mathematics and computer science). The deposited manuscripts are made accessible by the authors on these usually subject-specific servers before they have gone through a formal peer review process or even before they are submitted to a journal for publication. This is intended to facilitate a particularly rapid exchange of research results. A preprint server is a special type of repository, and in principle any repository can function as a preprint server. The best-known preprint server is arXiv, which has been in existence since 1991.

Publication funds

Publication funds are financial resources managed by scientific institutions which are used to cover publication fees. At Humboldt-Universität, there is a publication fund for journal articles and a publication fund for monographs and edited volumes.

Publication fees

Publication fees are charged for the publication of open access publications and are usually paid to the publishers or publishing institutions. This is usually the case for journal articles, which are subject to so-called article processing charges, or for books, which are subject to so-called book processing charges. They are usually paid by the employing institution or by research funding institutions on behalf of the authors.

Published version

The published version, also referred to as the publisher's version or version of record (VOR), is the version of a scientific publication that has been finally published and, in contrast to the previous manuscript versions (see preprint and postprint), has usually been formatted, typeset, and designed in a way that is uniform for the intended medium of publication. Accordingly, for journal articles, the published version is the official version of the article published by the journal.



A repository is a server connected to the internet for the orderly storage and archiving of electronic data. In science, such data can be publications, research data, and cultural heritage data. In most cases, a repository is associated with a scientific institution or has a disciplinary focus. The certified open access repository of Humboldt-Universität is the edoc-Server (more information).


Secondary publication

A work that was initially (see initial publication) published not open access but is made openly accessible in addition via another channel, either simultaneously or with a delay is called secondary publication (German: Zweitveröffentlichung). This complies with the principle of green open accessRepositories are most commonly used for this purpose. The version of the work deposited can be a manuscript version (see preprint and postprint) or the initially published version (see published version). In many cases, secondary publication is identical to self-archiving. We provide more information on secondary publication on a separate page.

Secondary publication right

The secondary publication right (or: right of secondary publication; German: Zweitveröffentlichungsrecht) refers to a provision in the German Copyright Act (§ 38 section 4, effective since 1 January 2014), according to which authors of scientific contributions have the irrevocable right to make these contributions publicly accessible in the accepted manuscript version (see postprint) twelve months after the initial publication, though only under certain conditions. We provide further information on the secondary publication right and how to exercise it on a separate page.


Self-archiving refers to the practice of depositing and archiving a version or copy of a previously published work, usually carried out by the author of the work. Repositories are most commonly used for this purpose. The deposited copies are almost always freely accessible, which complies with the principle of green open access. Manuscript versions are commonly deposited (see preprint and postprint), and less frequently the original, initially published versions (see published version). Self-archiving is in many cases identical to a secondary publication. We provide more information on self-archiving on a separate page.

Subscription model

In the subscription model, journals or other regularly appearing publications (or, the access to these) are purchased by libraries or other institutions via subscriptions. Accordingly, they are not freely accessible (see closed access). Frequently, it is no longer individual journals but entire journal selections of a publisher's portfolio that are the subject of a subscription (so-called journal packages or bundle deals).


Uniform Resource Name (URN)

A Uniform Resource Name (URN) is a persistent identifier for digital resources. By means of an identification number in the format urn:<namespace>:<ID>, a unique and permanent link to a digital resource is provided. The basic principle is that a resource can thus always be found, even if the actual target of this resource (usually a web address) changes. A comparable technical solution is the DOI system, which is most widely used in the scientific community.