Three Tiers of Words
Isabel L. Beck, Margaret G. McKeown, and Linda Kucan (2002, 2008) have outlined a useful model for conceptualizing
categories of words readers encounter in texts and for understanding the instructional and learning challenges
that words in each category present. They describe three levels, or tiers, of words in terms of the words’ commonality
(more to less frequently occurring) and applicability (broader to narrower).

While the term tier may connote a hierarchy, a ranking of words from least to most important, the reality is that all
three tiers of words are vital to comprehension and vocabulary development, although learning tier two and three
words typically requires more deliberate effort (at least for students whose first language is English) than does learning
tier one words.

• Tier One words are the words of everyday speech usually learned in the early grades, albeit not at the same
rate by all children. They are not considered a challenge to the average native speaker, though English language
learners of any age will have to attend carefully to them. While Tier One words are important, they are not the
focus of this discussion.

• Tier Two words (what the Standards refer to as general academic words) are far more likely to appear in written
texts than in speech. They appear in all sorts of texts: informational texts (words such as relative, vary, formulate,
specificity, and accumulate), technical texts (calibrate, itemize, periphery), and literary texts (misfortune,
dignified, faltered, unabashedly). Tier Two words often represent subtle or precise ways to say relatively simple
things—saunter instead of walk, for example. Because Tier Two words are found across many types of texts, they
are highly generalizable.

• Tier Three words (what the Standards refer to as domain-specific words) are specific to a domain or field of
study (lava, carburetor, legislature, circumference, aorta) and key to understanding a new concept within a
text. Because of their specificity and close ties to content knowledge, Tier Three words are far more common
in informational texts than in literature. Recognized as new and “hard” words for most readers (particularly
student readers), they are often explicitly defined by the author of a text, repeatedly used, and otherwise heavily
scaffolded (e.g., made a part of a glossary).