We intend this paper to be useful to a wide variety of people interested in any form of citizen science. We therefore explore the term ‘citizen science’ in a broad sense, including generation of any theory or hypothesis, research, scientific data collection, and/or data analysis in which the public (individuals or communities) participates. If readers prefer a different phrase for ‘citizen science,’ we encourage them to mentally substitute that phrase whenever we use the term here. Groups that are working to advocate and advance the development of citizen science, such as associations from around the world, may find our collection of terms and related starting points for discussion helpful for their own work on terminology, audience, and scope. 3 Our definitions and taxonomy of terms related to citizen science can be useful as a reference to students, guidelines for journal editors, and to inform academic scientists as they engage with the public. Finally, we hope this paper can be useful to policymakers, funders who seek to support citizen science, and participants in citizen science including managers, planners, and practitioners.

Although we intend to present some degree of consensus on terminology, we also seek to represent the diversity of our experiences, contexts, and perspectives. Not all of the opinions expressed in this paper are shared by all of the authors. We work in 11 countries around the world and represent a wide range of experiences with and commitments to citizen science (Table 1 ). Our terms, distinctions, definitions, and contexts originate from extensive collective experiences. While this paper does not exhaustively capture all perspectives of the larger citizen science community, we believe it is reasonably representative. We note, however, that most of the authors of this paper are academics and/or citizen science project leaders, many of whom are from the United States (U.S.) or Europe; we welcome comments from participants of and contributors to citizen science projects in other countries and regions.

Our discussions moved from the citsci-discussion list to an email thread with a more targeted group of contributors who were interested in pursuing the development of a paper on the topic of terminology. Leadership then emerged to facilitate the synthesis of our discussions (first author); a shared Google doc was used as a tool to document and refine our discussion. The topic of word choice (for ‘participants,’ ‘scientists,’ and ‘citizen science’) further expanded into the question of what citizen science is, reflecting the entanglement of terminology and ontology, i.e., what we call things is linked to what we think they are. This paper therefore begins by establishing contexts for citizen science terminology, then discusses what citizen science is (including relationships to other terms), next offers a starting point for discussions around terminology used for participants, and finally concludes with thoughts about balancing plurality with coherent shared practice.

This paper developed as a result of a lively conversation on the citsci-discussion-l email list, a Citizen Science Association (CSA) resource that was maintained by the Cornell Lab of Ornithology at the time this paper was developed. 2 Initially, one list member raised the question of what to call the people involved in a citizen science project:

Our primary goal for this paper is to discuss the contemporary terminology of science involving the public. To do so, we summarize contexts for citizen science and different ideas of what citizen science is, making connections with and distinctions among related terms. Our secondary goal is to raise questions regarding the terminology for citizen science participants. We therefore identify common terms used, particularly as they relate to different types of citizen science initiatives and contexts. Finally, we note that some groups may prefer to avoid the term citizen science altogether. Because less familiar terms may be less useful for mobilizing resources to develop and maintain projects (e.g., funding, volunteers, media buzz, legal precedent), we propose that the definition of ‘citizen science’ 1 be as broad as possible, making it available for diverse groups to claim if they choose. We also share our perspective on what citizen science is not and offer suggestions for how to maintain coherent shared practice while allowing for plurality. We intend our suggestions to apply broadly to any currently popular set of terms as well as any future terms that may be used to describe kindred forms of public participation in scientific research.

Terminology matters. People draw boundaries using language, choosing terms that include or exclude ideas, activities, and people ( Gieryn 1999 ). As a quickly evolving and still nascent field, citizen science is already a broad concept, and inclusion (in the sense of broadening participation in science) is central in many of its meanings ( Solomon 1993 , Irwin 1995 , Bonney 1996 ). Given this underlying tenet of inclusion, practitioners should give careful thought to the words they choose to describe activities, programs, and participants. Such care is important because terminology is also a part of how we construct our mental models of the world, what values we live by, and how we relate to each other ( Haraway 1988 , Barad 2007 ). Relationships between all members of research programs are particularly important for citizen science due to the large number of people involved, their varying motivations for involvement, and the power dynamics inherent in the way we produce knowledge. As an added challenge, terminology is never static and is constantly evolving. Terminology is particularly dynamic in citizen science, because the field is currently experiencing enormous expansion and a rapidly diversifying group of participants.

Background and Contexts for Citizen Science

To put our observations about citizen science terminology in perspective, we begin with a short discussion of how terminology matters, grounded in Science and Technology Studies (STS). We then review dictionary definitions of citizen science and provide some historical context. Finally, we discuss geopolitical and disciplinary contexts for the terminology of citizen science.

Theoretical Context: Why Words Matter Scholars of science argue that language is not merely representational. Instead, language and materiality are co-produced; that is, the words that we use for what we observe are fashioned simultaneously with our perceptions of what those things are (Haraway 1988). Language is a sensitizing concept, or in psychology terms, language can prime us to see certain things and not others. This entanglement extends further. Barad (2007) states that how we know about the world (epistemology), what we believe exists in the world (ontology), and the values by which we live our lives (ethics), are not separate. Because science is a way of knowing about the world, and because naming things is simultaneous with our ontological conception of what we are naming, the role of language in Barad’s (2007) entangled ethics/epistemology/ontology is a critical point for consideration in citizen science. Furthermore, language is an important part of the construction of what is considered science vs. not-science (‘boundary-work,’ Gieryn 1999). Citizen science is typically intended to broaden participation in science, so we are essentially in the business of redefining or even disassembling boundaries. Therefore, attention to the terminology we use is an important part of effective practice. Because citizen science is a form of knowledge production, citizen science terminology has the power to allow some peoples’ knowledge to be included and the knowledge of others to be excluded. This power potentially presents epistemic (knowledge) justice issues (Fricker 2007) and has consequences for the quality of our understanding of the world (Haraway 1988). As in many other participatory contexts, terminology can matter deeply to participants in citizen science projects. The terminology used to describe participants can potentially change the way they are treated or how they feel about themselves and their participation in the activity (Figure 1). The language used to refer to people, activities, and objects can have deep-seated resonance with racial inequities and histories of colonization. For example, the Standing Rock Sioux, as part of their resistance to the Dakota Access pipeline, object to being referred to as ‘stakeholders.’ Chairman Archambault said, “They would consider us a stakeholder, but we’re a nation” (quoted in Mufson 2016). Therefore, the use of terms like ‘stakeholder engagement’ is in conflict with how the Standing Rock Sioux view themselves, and in this case, the mismatch resulted in the tribe not participating in ‘stakeholder’ meetings. Or consider farmers in Colombia who, faced with social and armed conflict as well as militarized U.S.-Colombia anti-narcotics policy, are critical of the colonial legacies and capitalist influences of agricultural sciences (Lyons in press). Though these farmers conduct their own experimentation in their farming practices, they would not claim the term ‘citizen science’ to describe what they do when, for example, they use different ways of looking at and relating to soils than typical ‘scientific’ research. And in the U.S., the National Institutes of Health’s (NIH) International HapMap Project was designed to map human genome diversity from individuals around the world. Questions arose concerning what to label samples: If a sample was labeled ‘African’ or ‘Asian’ would the results be generalized as ‘all Africans’ or ‘all Asians?’ The NIH researchers spent considerable time and funding working with study participants to determine appropriate names, despite concerns that names could reproduce racial biases. Ultimately, the names suggested by participants were not used (Reardon in press). Finally, as boundary-work, terminology selection is inherently strategic. This issue has been a part of our group’s discussions and has revealed our diversity of opinions. Some terms may be better for egalitarian purposes of democratizing knowledge production, while others may be better used for establishing the validity of citizen knowledge and authority to policy-makers. Still other terms are appropriate when working with indigenous people. We all came to this project with different goals in mind, and our orientations regarding terminology reflect this diversity. Different terms serve different goals, and different terms are appropriate for different audiences–e.g., prospective participants in projects vs. skeptical policy-makers vs. academics defending the concept of value-free science. In many ways, the range of goals and associated terms reflects the expansion of contemporary science beyond professional boundaries to include many facets of civil society.

Dictionary Definitions and the ‘Two Strands’ of Citizen Science In regard to definitions of terms, which activities fall under the guise of ‘citizen science’ is both nuanced and in a state of flux, although it is generally agreed that citizen science refers to the inclusion of members of the public in some aspect of scientific research. While the term ‘public’ or ‘the public’ is often used to describe the general population, well established research in public understanding of science and public engagement reminds us that the public cannot be assumed to be a monolithic entity (Chilvers and Kearnes 2015; Marres 2007). The term ‘citizen science’ was added to the Oxford English Dictionary in 2014 as “Scientific work undertaken by members of the general public, often in collaboration with or under the direction of professional scientists and scientific institutions” (OED 2016a). This definition of citizen science fails to consider the broader use of the term as initially coined by Alan Irwin (1995). Cooper and Lewenstein (2016) discuss these two meanings or ‘strands’ of citizen science. The first strand, from Irwin’s definition, emphasizes the responsibility of science to society, which they call “democratic” citizen science. At the other end of the spectrum they position the second strand, “participatory” citizen science, as practice in which people mostly contribute observations or efforts to the scientific enterprise, a meaning that originated with Rick Bonney’s (1996) work at the Cornell Lab of Ornithology. Bonney et al. (2016) suggest that future iterations of the OED definition should highlight the diversity, scale, and value of citizen science projects from both strands. Ceccaroni et al. (2017) focus on the convergence of these viewpoints to define citizen science in relation to civic education as work undertaken with citizen communities to advance science, foster a broad scientific mentality, and/or encourage democratic engagement, which helps society address complex modern problems. Citizen science terms are dynamic and change over time, therefore “it would be a shame for us to ignore widespread public interpretations of key terms and the reasons for those interpretations.” (Daniela Soleri, personal communication) In that vein, using the word ‘citizen’ also can be an issue, as this word may be defined as “A legally recognized subject or national of a state” or “An inhabitant of a city or town” (OED 2016b). The first definition is problematic in some parts of the world where legal recognition is complex, and legal citizenship may not be relevant in many citizen science projects. The second definition appears to prioritize urban inhabitants. Citizenship can be more broadly construed, but the term remains problematic in practice; these difficulties also vary by country. While we cannot erase the potential problems associated with the term and we understand that many community members may not want to be called ‘citizens,’ in this paper we use the word ‘citizen’ as part of ‘citizen science’ because the term is familiar to most, and define ‘citizen’ here to mean a member of a broadly construed community.

Historical Context for Professional and Citizen Science The term ‘scientist’ was coined in 1833 (Yeo 1993) and slowly grew in use. The Eurocentric scientist-as-profession paradigm is relatively new, emerging slowly throughout the 17th to 19th centuries. Initially called ‘philosophers of science’ or ‘natural philosophers,’ individuals who pursued research made their living in another profession, were sponsored by a benefactor, or had independent means. Truth was accepted from “gentlemen” as reliable, in contrast to other groups, and technicians in gentlemen’s labs were regarded as “invisible” (Shapin 1994). Sometimes these early scientists investigated topics by recruiting others through peer networks to assist with data collection and/or analyses (Miller-Rushing et al. 2012). For example, Charles Darwin was not a professional researcher but an unpaid companion on the Beagle, though he had medical training (Silvertown 2009). In 1874, many governments engaged prominent astronomers around the world to measure the Earth’s distance to the Sun in the “Transit of Venus” project (Ratcliff 2008). Some individuals outside the gentry also were able to contribute to discoveries. For example, Mary Anning–who had no training initially–found the first British Ichthyosaur (among other fascinating fossils) and became one of the most influential women in British paleontology, particularly posthumously (Hall 2002). Citizen science as participatory data collection (part of Bonney’s 1996 definition) has existed for a long time without specific descriptive terminology. Members of the public have collected observations of nature for hundreds of years in such fields as archaeology, astronomy, and natural history (Silvertown 2009). In the late 1800s, amateurs were valued only for their observations rather than their ability to elucidate meaning from observations. An attitude prevailed that all observations, fossils, specimens, and so forth should be brought to a central place in England so that ‘scientists’ could use the materials and information to generate knowledge and advance science. So even after scientific research was professionalized and institutionalized, a partnership occurred between amateur and professional scientists (Miller-Rushing et al. 2012), although in some disciplines such as veterinary science, the quality of information collected by amateurs was progressively viewed with skepticism (Ruth Duerr, personal communication). In many cases, citizen science is often viewed through this lens of a partnership between amateur data collectors and professional elucidators. As another example, the Audubon Christmas Bird Count in the U.S. was founded in 1900, and the United Kingdom (U.K.) also has a long and rich history of wildlife recording by volunteers; such existing programs are now labeled as ‘citizen science,’ which contributes to the recent perceived and actual rise in citizen science projects (Roy et al. 2012). ‘Citizen scientist’ (meaning scientist independent of institutions) was used at least as early as 1912 (Scott 1912). ‘Participatory Action Research’ (PAR), also termed ‘Community Action Research’ (CAR), became popular during the social movements in the 1960s and 1970s, especially in Latin America (McTaggart 1991, Torres 1992, Kindon et al. 2008). ‘Citizen science’ as a democratic concept was used in the 1990s (Solomon 1993; Irwin 1995), around the same time that Bonney first used ‘citizen science’ to describe his long-running participatory data collection projects (1996). ‘Crowdsourcing,’ as a term to describe an open call to a wide group to aid in some kind of labor, originated in WIRED magazine in a 2006 article; even in this first use, the term included examples of crowdsourced science and research (Howe 2006).

Disciplinary and Sectoral Context Citizen science is associated with, and often overlaps with, a variety of other names that may align with the context of an activity–such as the academic discipline, geopolitics, language, and culture–or features of research design, such as modes of engagement. In public health and environmental justice contexts, for example, ‘community-based participatory research’ (CBPR) is more commonly used (see, for example, Minkler and Wallerstein 2011), and terms for participants tend toward ‘resident,’ ‘neighbor,’ or ‘community member.’ Jason Corburn (2005) very carefully chooses the term ‘local knowledge’ for his study of community-based public health research. In geography, ‘volunteered geographic information’ is commonly used to describe engagement of large numbers of participants involved in the digital creation of geographic information (Goodchild 2007; Sieber and Haklay 2015), and despite the term’s focus on data, it is widely used to describe the ‘citizen science’ activity itself. The term ‘participant’ in medical research may refer to those participating in studies as human subjects of research, which contrasts with how the term is typically used in citizen science projects. Differences in disciplinary contexts, vocabularies, and norms may make it difficult for researchers in one discipline to understand the engagement practices, methods, data, and impacts of researchers in another discipline. These differences also may create confusion among participants about the type and depth of their own involvement in the project. In some cases, developing standardized vocabularies for citizen science which articulate shared aspects, such as quality assurance/quality control concerns, may transcend disciplinary differences (Ceccaroni et al. 2017). However, these shared vocabularies must be co-developed by, and later used by, a wide range of relevant stakeholders.