Vocabulary on Borrowed Time: Which LCSH Headings May Not Survive the Next Two Decades

Predicting which words will outlast their usefulness is, in some respects, a fool's errand. Controlled vocabulary professionals have learned through hard experience that the terms most likely to age poorly are rarely the ones that seem obviously problematic at the time of their creation. The headings that looked perfectly reasonable in 1975 and read as dated or offensive today were not, for the most part, the subject of vigorous debate when they were established. They were the unremarkable consensus choices of their moment—which is precisely why they persisted unchallenged for so long.

With that caveat firmly in place, the exercise of identifying today's potentially vulnerable headings is not merely speculative. It is a form of institutional self-examination that the cataloging profession benefits from conducting periodically, and it is more rigorous than it might appear. Historical patterns of heading obsolescence, combined with an understanding of the social, technological, and political forces currently reshaping knowledge, allow for reasoned analysis of which categories of LCSH vocabulary carry the highest terminological risk over the next twenty years.

What History Teaches About Heading Longevity

Retired and revised LCSH headings fall into recognizable patterns. The most common categories of obsolescence include:

Terminology reflecting superseded scientific consensus. Headings built around diagnostic categories, species classifications, or physical science terminology that has since been revised by the relevant professional communities. The history of mental health headings in LCSH is particularly instructive here: terms that once reflected clinical consensus have required repeated revision as the Diagnostic and Statistical Manual of Mental Disorders has been updated and as patient advocacy communities have successfully challenged pathologizing language.

Terminology encoding social hierarchies that later generations rejected. These are the headings that generate the most public attention when they surface—terms that reflected the assumptions of a predominantly white, male, anglophone institutional culture and were eventually challenged as those assumptions came under scrutiny.

Technology-specific terminology that became obsolete faster than the catalog could adapt. Headings built around specific hardware, software, or media formats that were superseded by technological change. The catalog's historical record contains headings for technologies that no longer exist in recognizable form, preserved in bibliographic records that now function more as artifacts than as retrieval tools.

Political and geopolitical terminology that became inaccurate. Headings referencing nations, governments, or political entities that no longer exist in their cataloged form, or whose names have changed as a result of decolonization, political transition, or community reclamation.

Each of these categories is actively generating new candidates for future obsolescence within the current LCSH vocabulary.

Technology Headings: A Particular Vulnerability

The velocity of technological change makes technology-related headings among the most structurally precarious in the current authority file. Headings that name specific platforms, devices, or technical architectures are particularly exposed. Consider Smartphones—a heading that reflects a device category currently dominant but whose long-term stability as a distinct consumer technology form is uncertain as computing continues to migrate into wearable, ambient, and embedded contexts. The heading may survive in revised form, or it may eventually be absorbed into a broader heading for personal computing devices that encompasses form factors not yet commercially available.

More immediately vulnerable are headings built around the current vocabulary of artificial intelligence and machine learning. Terms like Machine learning and Neural networks (Computer science) are well-established in the authority file, but the subheadings and compound headings being established to describe specific applications and architectures—Large language models, Generative adversarial networks—reflect a technological moment that is evolving rapidly. The terminology that researchers and practitioners are using in 2025 may look as dated in 2045 as Expert systems (Computer science) looks today.

Social and Political Terminology Under Pressure

Social movement vocabulary presents a different kind of risk. Headings established to describe contemporary social phenomena carry the dual vulnerability of reflecting both contested political terrain and rapidly evolving community self-identification practices.

The heading Black Lives Matter movement is a case study in this tension. Established relatively recently to describe a significant and ongoing social movement, it reflects a specific historical moment in American political life. Whether the heading will remain stable, require subdivision or disambiguation, or eventually be absorbed into broader headings related to civil rights or racial justice activism depends on how the movement itself evolves and how future catalogers assess its historical significance. The heading is not wrong; it is, by definition, time-bound in ways that will only become fully apparent in retrospect.

Similarly, headings built around the current vocabulary of gender identity and sexual orientation are operating in a domain of active terminological evolution. The cataloging community has worked in recent years to update headings in this area to reflect contemporary community usage—a process that is ongoing and that will almost certainly require continued revision as language continues to shift. Metadata professionals working in this domain are candid about the likelihood that some of today's carefully chosen terms will require revision within the next decade, let alone twenty years.

The Opinion of Practitioners

Librarians and metadata professionals who work closely with LCSH tend to identify a few specific characteristics that predict heading instability. Headings that are highly specific to a current event or a named individual associated with a living movement carry obvious risk. Headings that reflect a single discipline's current terminology in a fast-moving field—computational biology, climate science, digital humanities—are vulnerable to being outpaced by the field's own evolving vocabulary. And headings that have been established without robust community input from the people they describe carry the particular risk of being challenged and revised as those communities gain greater voice in cataloging processes.

One recurring observation among practitioners is that headings established reactively—in response to urgent cataloging needs created by high-volume acquisitions in a new area—are more likely to require later revision than headings developed through the standard proposal and review process. Speed and terminological stability are not natural allies.

What Replacement Patterns Reveal

Perhaps the most instructive aspect of anticipating heading obsolescence is not identifying which specific terms will be retired but recognizing what their eventual replacements will likely reflect. If historical patterns hold, the headings that replace today's vulnerable terms will tend to be more specific, more community-centered in their language, and more reflective of the perspectives of the people and phenomena being described.

That trajectory is, in itself, a form of institutional progress—slow, incremental, and imperfect, but directionally consistent. The catalog of 2045 will almost certainly look back at some portion of today's authority file with the same mixture of recognition and discomfort that today's catalogers feel when they encounter the vocabulary of fifty years ago.

The professional value of this exercise is not prediction for its own sake. It is the cultivation of a disposition toward the present vocabulary that holds current choices accountable to future revision—a recognition that every heading established today is, in some sense, a loan from the future, and that the terms of repayment are not yet known.