Lexical Density and Nominalization

The ratio of content words (nouns, adjectives, verbs, and adverbs) to function words (pronouns, prepositions, auxiliary verbs, determiners, exclamations, and conjunctions) is called lexical density. More content words mean greater density. Compared to typical narrative texts that students read, textbooks tend to have high lexical density, with more challenging vocabulary that defies skimming. Students need to learn what the words mean, but even if they know the vocabulary they must learn to read dense text relatively slowly, breaking, annotating, reflecting, and rereading.

Nominalizations increase lexical density. 

Nominalization is the morphological process by which we take verbs or adjectives and turn them into nouns. This allows the writer to express certain kinds of ideas very efficiently, packing a lot of information into a single word. Examples of nominalizations include: demonstration (changing the verb demonstrate to a noun), intention (verb = intend), argument (verb = argue), or intensity (adjective = intense).

Compressing Language and Concepts into Words

Here are two examples of different lexical densities:

"Gutenberg invented moveable type. Moveable type made it possible to print lots of books cheaply. When there were cheap copies of books, it meant that books could be sent far away. Libraries could all have copies, and there were enough books that people could buy and sell them. As a result, more people could learn about new things and other places." 

That same information might appear in a textbook in a less narrative, more efficient form:

"The invention of moveable type facilitated the dissemination of information through printed books." 

This version has lots of academic language features, in particular the nominalizations invention, dissemination, and information, that compress into a few words the ideas that otherwise required several sentences to be explained.