What is lexical density?

Lexical density is a term used in discourse (or text) analysis. It is used to measure the ratio of content words to grammatical words in any given text (spoken or written).

Content words comprise the nouns, adjectives, most verbs (i.e. all except 12 special verbs) and most adverbs (e.g. 'beautifully' but not 'here', which is a pro-form and = (means) 'in this place').

Grammatical (or functional) words comprise pronouns, prepositions, conjunctions, 12 special (auxiliary) verbs (e.g. can, could), some adverbs (used as pro-forms), determiners (e.g. a, the, my) and interjections (ouch).

The average ratio in a 100-word text is 50:50 (expressed as 0.5).

If the content ratio is high (e.g. 0.7), then the text is very probably quite a complicated written text, e.g. a specialised academic text.

If the content ratio is low (e.g. 0.3), then the text is probably a spoken text and hopefully easy to understand depending on the situation, and the speaker's ability to speak coherently and in a recognisable dialect.