> ## Documentation Index
> Fetch the complete documentation index at: https://docs.consensus.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Track how a field's terminology changed over time

> Compare old and recent literature on the same concept so you search the terms the field actually used, not just the ones it uses now.

## What you get

A mapping of old vocabulary to current vocabulary for your topic, a note on when the shift happened, and a search-term list covering both — so a review does not silently miss its own foundational literature.

## Who it's for

Anyone entering an unfamiliar field, and every systematic reviewer, where missing older work is a methodological failure rather than an inconvenience.

## Why this matters more than it sounds

"Gut flora" became "gut microbiome". "Manic depression" became "bipolar disorder". "Mental retardation" became "intellectual disability". Search only the current term and the foundational decade of a literature is invisible to you — and nothing in your results indicates it is missing.

This is one of the few review failures that produces no error signal at all.

## How it works

<Steps>
  <Step title="Run the same concept in two eras">
    One search with `year_max` set before the suspected shift, one with `year_min` set after. Same concept, deliberately different windows.
  </Step>

  <Step title="Extract the vocabulary from each window">
    Pull the recurring noun phrases from titles and abstracts in each set. You are comparing how the field named the thing, not what it concluded.
  </Step>

  <Step title="Find the crossover">
    Narrow the window year by year to locate when the new term overtook the old. That date is worth reporting — it tells later readers where your search boundary sits.
  </Step>

  <Step title="Check whether the concepts are actually identical">
    Terminology changes sometimes accompany a definitional change. "Gut flora" and "gut microbiome" are close to interchangeable; other renamings narrowed or widened what counts. Say which case applies.
  </Step>

  <Step title="Build the combined term list">
    Produce a single list with both vocabularies and an era note on each, ready to paste into any search.
  </Step>
</Steps>

## The API calls

```bash theme={null}
# older window
curl -G "https://api.consensus.app/v1/search" \
  -H "x-api-key: $CONSENSUS_API_KEY" \
  --data-urlencode "query=intestinal bacteria host metabolism" \
  --data-urlencode "year_max=2010" \
  --data-urlencode "page_size=100"

# current window
curl -G "https://api.consensus.app/v1/search" \
  -H "x-api-key: $CONSENSUS_API_KEY" \
  --data-urlencode "query=gut microbiome host metabolism" \
  --data-urlencode "year_min=2021" \
  --data-urlencode "page_size=100"
```

Beyond vocabulary, the two windows also reveal **conclusion shifts** — where older papers reached different findings, signalling a paradigm change or accumulating evidence — and **methodological evolution**, where observational work gave way to trials and then to meta-analyses. Both tell you how mature the evidence base is.

## What to check before you trust it

* **Confirm the old term actually returns results.** A term that returns nothing may be wrong rather than obsolete; check it against a paper you know exists.
* **Watch for terms that were never synonyms.** Adjacent-but-different concepts appearing in the old window will pull irrelevant work into your review if you treat them as equivalent.
* **Note regional and disciplinary variation.** Some vocabularies split rather than shift, and both remain current in different communities.
* **Record the term list in your methods.** It is part of the search strategy, and a reviewer who spots a missing synonym will ask.

## Related

<CardGroup cols={2}>
  <Card title="Build a reusable literature-review workflow" icon="wand-magic-sparkles" href="/use-cases/literature-review-skill">
    Era-gated searches as one step in a full review.
  </Card>

  <Card title="Build a PRISMA-ready search corpus" icon="layer-group" href="/use-cases/prisma-corpus">
    Where a missed synonym does the most damage.
  </Card>

  <Card title="Best practices" icon="shapes" href="/use-cases/best-practices">
    Filter ladder and the rest of the primitives.
  </Card>

  <Card title="All use cases" icon="grid-2" href="/use-cases">
    Browse the gallery by persona.
  </Card>
</CardGroup>