Understanding Corpora Tables discusses different ways of counting and categorizing words in corpora. It outlines tokens, types, lemmas, word families, and frequency levels. High frequency words consist of around 2,000 word families and make up 90% of coverage. Mid-frequency words are around 7,000 families and cover 9%. Low frequency words are around 50,000 words and cover just 1%. Nation's work on vocabulary frequency is referenced.