What a word frequency list shows
A frequency list counts every word in a text and sorts the words from most to least frequent. In almost any English text the top of the list is made of function words such as the, of and and; turn on "Hide common words" to see the content words that tell you what the text is about.
With "Group by lemma" on, inflected forms are counted together: study, studies, studied and studying become one row for study. This is usually what learners and teachers want; turn it off to count each spelling separately.
How learners, teachers and writers use it
- Learners find the key vocabulary of a text before reading it. Words that appear five or more times in a chapter are worth learning first.
- Teachers build vocabulary lists from course texts and check how often target words are recycled.
- Writers and students spot overused words in essays and see whether their vocabulary is varied enough.
- Researchers get a quick frequency profile and a CSV for further analysis.
Lexical diversity: TTR and the Guiraud index
Type-token ratio (TTR) divides the number of different words (types) by the total number of words (tokens). A TTR of 0.5 means that, on average, every word appears twice. TTR falls as texts get longer, because common words keep repeating, so only compare texts of similar length.
The Guiraud index (types divided by the square root of tokens) is less sensitive to length. Higher values mean a richer vocabulary; for short texts, values above about 7 are typical of varied writing.
Coverage by the most frequent words
The coverage figures show what share of the text is made of the 1,000, 2,000, 3,000, 5,000 and 10,000 most frequent English lemmas. In everyday English, the top 1,000 lemmas usually cover around 75–85% of a text and the top 3,000 around 90%.
For a learner, coverage is a quick difficulty measure: if you know roughly the top 3,000 words and the text's 3,000-word coverage is 97%, you will meet about three unknown words in every hundred. The text difficulty checker turns this into a verdict for your level.
Rare words
Rare words are lowercase words ranked beyond the 10,000 most frequent English lemmas, or not in the list at all. In a novel they are often the most interesting words; in an essay they may be jargon worth explaining. Names are excluded.
