Corpus

• Zipf's Law

  Empirical observation that term frequency is inversely proportional to frequency rank; explains why few words dominate corpus.

• Vocabulary

  Set of unique terms appearing in a corpus; fundamental to information retrieval and language analysis. Distinguished from types and tokens.

• Heaps' Law

  Vocabulary grows sub-linearly with corpus size; predicts vocabulary size from token count via power law.

• Hapax Legomenon

  Term occurring exactly once in a corpus; indicates vocabulary richness and poses challenges for language models and IR systems.