Heaps' Law

An empirical relation between tokens N and observed vocabulary size V(N) commonly expressed as V(N) = K · N^β (with constants K>0 and 0<β<1 for many natural language corpora), meaning vocabulary grows sublinearly with text length.

An empirical relationship observed in text corpora that the number of distinct word types V(N) grows sublinearly with the total token count N and is commonly modelled as V(N) ≈ K · N^β with 0 < β < 1 and constant K depending on language and tokenization. It characterizes diminishing rates of new vocabulary discovery as a corpus grows.