oncedistinct

Oncedistinct is a neologism used in discussions of identity within temporal or context-dependent frameworks. It denotes a specific kind of distinction between two entities: they are not the same object, but they differ in exactly one context or time point, and are indistinguishable in all other relevant contexts. In temporal models, two objects a and b are oncedistinct if there exists a unique time t0 such that a and b differ with respect to a chosen distinguishing predicate P at t0, and for every other time t ≠ t0, a and b agree on all predicates under consideration. This captures a pattern of discernibility that is sharped by a single distinguishing moment, after which the two entities are treated as distinct but otherwise identical within the model.

Examples: In a dataset, two records may have identical fields across all timestamps except in one timestamp where the values diverge due to a logging error; in a narrative, two character identities may be functionally the same in all scenes except one crucial scene where one uses a different alias.

Etymology and usage: The term combines 'once' and 'distinct'. It is not widely standardized and appears primarily in theoretical discussions of identity and temporal logic, as well as in some data deduplication literature. It remains a niche concept with variable definitions across authors.

See also: Identity, Indiscernibility, Temporal logic, Distinction, Data deduplication.

References: The term is relatively new and not widely adopted; readers may encounter it in selective philosophical or technical discussions rather than formal textbooks.