Hallucination
Fluent, confident output that is not supported by the input or by evidence.
By Lattice editorial · Entry last reviewed · method
What it implies
Usually discussed as a model property. In practice it is overwhelmingly a *retrieval* and *verification* problem: the model was not given the fact, or was not asked to check. Constrained decoding, citation requirements and abstention do more than any amount of prompting.
Related terms
- Context windowThe number of tokens a model can consider at once — a ceiling on what you can send, not a target for what you should.
- Recall@kOf the documents that should answer a query, the fraction that appear in the top k retrieved.
- Validation and repairGenerating freely, then validating the output against a schema and retrying with the error fed back.