Definition
Plain language
The known-correct answer used as the yardstick for grading whatever the system produced.
As stated in the literature
Reference labels or values treated as authoritative for evaluation or reward computation; in verifier and benchmark design, often embedded as privileged information the system under test cannot see.
Also called: ground-truth
Why it matters: Without a trusted reference answer, there is no reliable way to score whether a system's output is right or to train it toward correctness.
For example, when grading a model's answer to '2+2', the ground truth is the known-correct '4' that its output is compared against.
Heard on the show
“Things where there's no factual ground truth — just contested takes.”Episode 004 — The Sycophancy Circuit That Survives Alignment Training