Lexical density

Writing Tips >> Lexical Density

The types of vocabulary used in a piece of writing, and how complicated a text is, can be described through different measures. One of the popular measures is Lexical Density which literally means how “dense” a lexicon is.

A major principle behind Lexical Density is that vocabulary can be classified into two types – lexical/content words and functional/grammatical words. Assessed with Lexical Density, a piece of writing is regarded as “dense” if it consists of many lexical words relative to its total number of words.

Lexical words refer to adjectives, adverbs, nouns, and verbs. Adjectives modify nouns while adverbs modify verbs. These four classes of words are considered “lexical” because they convey information and constitute the meaning of a text.

Functional words include all other classes of words such as articles, auxiliary verbs, and prepositions. These words mostly reflect the structural features rather than the meaning of a text.

The lexical density in a text can be expressed in the form of a percentage as shown in the following formula.

Number of lexical words x100 / Total number of words

Below are two sentences in which lexical words are highlighted in red. Sentence A contains 6 lexical words out of all the 7 words; Sentence B contains 7 lexical words out of all the 12 words.

Sentences Formula Lexical Density
A.     Adjectives modify nouns while adverbs modify verbs. 6 x100 / 7 85.71%
B.     Adjectives are used to modify nouns while adverbs are for describing verbs. 7 x 100 / 12 58.33%


The above examples demonstrate how two sentences can be compared in terms of lexical density. Sentence A achieves a higher Lexical Density (85.71%) as compared to that of Sentence B (58.33%). Sentence A is therefore considered “denser”.

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