Blog Series

Vocabulary and Oral Language: The Keys to Comprehension

by Dr. Kelly A. Powell-Smith on Oct 22, 2019

  • Assessment
  • Vocabulary
Dr. Kelly A. Powell-Smith

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Comprehending written text is an essential life skill. Consider all the ways you use your reading comprehension skills in everyday life. Everything from reading comics in the newspaper and social media to reading the voter's pamphlet or reading a job application are impacted. Because of its importance, school personnel need to understand which reading skills are critical to the development of reading comprehension.

It probably won't come as a surprise that reading comprehension is a complex process consisting of several component skills and processes that work together in an integrated fashion. As such, when it comes to understanding reading comprehension problems, we need to untangle the variety of reasons why a student might struggle. Some of those reasons might include poor basic skills in phonemic awareness, decoding, or text reading fluency. While students may exhibit reading comprehension problems for a variety of reasons, two key areas are vocabulary and oral language.

What is the Significance of Vocabulary and Oral Language Development?

  • Vocabulary is one of the largest contributors to reading comprehension skill. Work by Stahl & Nagy (2006) suggests that vocabulary knowledge contributes 50 percent to 60 percent of the variance in reading comprehension outcomes.
  • Early vocabulary development fosters development of other critical basic skills (e.g., phonological awareness).
  • Children with more poorly developed vocabulary show declining comprehension skills later in elementary and middle school.
  • Oral language is a fundamental building block for learning. Children who come from a rich spoken language environment often have less difficulty comprehending text.

In What Ways Does Vocabulary Impact Comprehension?

Vocabulary impacts comprehension directly with respect to the understanding of text and indirectly because knowing a word's meaning impacts word recognition fluency. An advantage of a strong vocabulary is that the more words you know, the easier it is to understand text and become fluent while reading. Reasons why include:

  • When a student has heard a word before, it makes it easier for them to map the letters in the word to the sounds of the word.
  • Knowing something about what a word means may help a student recognize the word in text, which contributes to their overall understanding of the sentence and passage in which it appears.
  • Breadth of vocabulary knowledge is related to background knowledge. Greater background knowledge helps students comprehend more challenging text.

Other Oral Language Skills Critical for Comprehension

While vocabulary is one of the largest contributors to comprehension, among the other oral language skills critical for students to develop are knowledge of syntax and morphology. Syntax involves the understanding of the order of words and their relationship to other words in a sentence. Morphology involves the knowledge of word parts or the smallest units of our language that can change the meaning of a word.

Ways knowledge of syntax aids student comprehension include greater ease with:

  • Chunking sentences into meaningful units.
  • Making sure decoding is accurate so they can fix decoding errors quickly and not disrupt the flow of their reading.
  • Verifying the meaning of unfamiliar words.
  • Clarifying meaning of ambiguous words, or words with multiple meanings.

Ways knowledge of morphology aids student comprehension include:

  • Increased vocabulary as students make connections between root words and the new words created by adding prefixes and suffixes (e.g., act + ion = action; re + act = react; re + act + ion = reaction).
  • Increased knowledge of syntax and grammatical understanding.
  • Increased fluency in reading connected text, which frees up cognitive resources that can then be allocated for comprehension.

So how might we pinpoint student difficulties in these key skill areas? One way to do so is by using diagnostic assessments that directly assess them and can be linked to targeted intervention. Pinpointing instructional needs in these critical areas can provide students the keys to unlocking the power of reading comprehension.

An Example: Acadience Reading Diagnostic:
Comprehension, Fluency, & Oral Language

A primary purpose of AcadienceReading Diagnostic: Comprehension, Fluency, & Oral Language (CFOL) is to assist educators in (a) untangling the many possible reasons why a student may struggle with comprehension and (b) better targeting interventions to those skill areas that support reading comprehension. As such, CFOL includes tasks in these skill domains: Story Coherence and Text Structure, Listening Comprehension, Reading Comprehension, Syntax and Grammar, Morphological Awareness, Vocabulary and Word Knowledge, and Reading Fluency.

For more information about Acadience Reading Diagnostic: CFOL, visit here.

About the Author

Dr. Kelly A. Powell-Smith is Vice President and Associate Director of Research & Development at Acadience Learning, where she conducts research on assessment and intervention related to early childhood language and literacy development. Dr. Powell-Smith, a nationally certified school psychologist, obtained her doctorate in school psychology from the University of Oregon. She is a former Associate Professor of School Psychology at the University of South Florida. She was a faculty associate of the Florida Center for Reading Research (FCRR) and a consultant with the Eastern Regional Reading First Technical Assistance Center (ERRFTAC). She has provided training in formative assessment and academic interventions in 22 states and Canada. Dr. Powell-Smith has conducted research related to children with various learning and behavioral difficulties, has served on the editorial boards for School Psychology Review, Psychology in the Schools, School Psychology Forum, Journal of Evidence Based Practices for Schools, and Proven Practice in the Prevention and Remediation of School Problems, and has conducted over 230 national, state, and regional workshops and presentations.


Stahl, S. A., & Nagy, W. E. (2006). Teaching word meanings. Mahwah

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