Blog Post··18 min read
From Likelihood to Perplexity: One Unified Reference
Probability, likelihood, log-likelihood, NLL, expectation, entropy, cross-entropy, KL divergence, and perplexity are constantly confused for one another. They are not the same thing — but they are all the same thing seen from different angles. This is the definitive deep-dive that names each one precisely and shows exactly how they connect for LLMs.