WordBank Glossary

Phrase	Description
Academic words	Words used more frequently in textbooks or other academic contexts and not as frequently in oral language or narratives. Academic words can be general or domain-specific.
Bias	The extent (indicated by a value between -1 and 1) to which a word’s use is concentrated within a particular domain. There are four measures, one for each domain in the corpus (science, math, social studies, and reading/ELA). A bias value above zero means that a word occurs more in that particular domain than in other domains. A negative value indicates that the word appears less in that domain. All four bias measures will sum to zero because if a word occurs more in one domain, it must also occur less in one or more other domains.
Dispersion	The extent (indicated by a value between 0 and 1) to which a word is spread across the textbooks that in the corpus. A value near 0 indicates the word occurs mostly in one textbook. A value near 1 indicates that the word is used across many textbooks within and across domains.
Frequency	The expected number of specific word encounters a student will have (given a grade range and or a domain) based on text in the Corpus.
Landscape of American School English Corpus	Comprised of over 40 million running words from 144 best-selling K-12 textbooks in science, math, social studies and reading/English language arts from 2011 to 2015. This corpus reflects words that K-12 students in the U.S. will encounter in their studies. Unlike most corpora in use today, it references materials intended primarily for students rather than adults.
Lexile Word Measures	A Lexile word measure is an estimate of the challenge a particular word will present, on average, to a particular reader during independent reading.
Running and Unique Words	“Unique words” can be contrasted with “running words” because while the same word may be repeated many times in a text, it counts as only one “unique” word with many “running” occurrences or repetitions. The technical terms type (unique word) and token (running word) are also often used.

Academic words

Words used more frequently in textbooks or other academic contexts and not as frequently in oral language or narratives. Academic words can be general or domain-specific.

Bias

The extent (indicated by a value between -1 and 1) to which a word’s use is concentrated within a particular domain. There are four measures, one for each domain in the corpus (science, math, social studies, and reading/ELA). A bias value above zero means that a word occurs more in that particular domain than in other domains. A negative value indicates that the word appears less in that domain. All four bias measures will sum to zero because if a word occurs more in one domain, it must also occur less in one or more other domains.

Dispersion

The extent (indicated by a value between 0 and 1) to which a word is spread across the textbooks that in the corpus. A value near 0 indicates the word occurs mostly in one textbook. A value near 1 indicates that the word is used across many textbooks within and across domains.

Frequency

The expected number of specific word encounters a student will have (given a grade range and or a domain) based on text in the Corpus.

Landscape of American School English Corpus

Comprised of over 40 million running words from 144 best-selling K-12 textbooks in science, math, social studies and reading/English language arts from 2011 to 2015. This corpus reflects words that K-12 students in the U.S. will encounter in their studies. Unlike most corpora in use today, it references materials intended primarily for students rather than adults.

Lexile Word Measures

A Lexile word measure is an estimate of the challenge a particular word will present, on average, to a particular reader during independent reading.

Running and Unique Words

“Unique words” can be contrasted with “running words” because while the same word may be repeated many times in a text, it counts as only one “unique” word with many “running” occurrences or repetitions. The technical terms type (unique word) and token (running word) are also often used.