# referential opacity

CEFR C2 · Noun

Source: https://englishreference.com/word/referential-opacity
Updated: 2026-09-28

## Definition

a linguistic puzzle where swapping two words that mean the same thing changes whether a sentence is true.

For teachers: a semantic property of linguistic contexts in which substituting co-referential expressions (terms referring to the same object) can alter the truth value of the proposition.

## Examples

- Believing that Superman saved the day shows referential opacity if someone does not know that Superman is Clark Kent.
- Knowledge graphs must navigate referential opacity when modeling what specific agents believe versus objective reality.
- Epistemic logic incorporates modal operators to formalize referential opacity, preventing automated theorem provers from drawing fallacious substitutions.

---

From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.