Wednesday, May 31, 2023

Vocabulary acquisition is an essential part of language learning. A robust vocabulary equips students to comprehend and write texts that are complex, detailed, and specific. On the flip side, students who lack foundational word recognition skills often struggle to comprehend what they read (Gough et al. 1981; Stanovich 1980). Thus, it is important that we empower students with the tools they need to successfully decode and understand unfamiliar words. And according to the large body of evidence that makes up the science of reading, there is more to vocabulary learning than simply memorizing new terms with flash cards or guessing words from context. Vocabulary must be taught explicitly and systematically, in a way that engages all of the parts of the brain associated with word recognition. One way to do this is through the POSSUM (phonology, orthography, syntax, semantics, understanding, and morphology) approach, a vocabulary instructional tool that supports the development of word recognition skills in the brain.

Word Recognition in the Brain

For many strong readers, the process of seeing and recognizing a written word is automatic. However, our brains actually have to activate a complex series of neural pathways in order for word recognition to occur. These neural pathways are associated with several areas of the brain.

One of these areas is the phonological processor, which is located in the back part of the frontal lobe of the brain (Moats & Tolman, 2009). Its job is to process the speech sounds of language, which are called “phonemes.” This region of the brain is necessary for oral language to be produced and received.

Illustration of the phonological processor in the brain, with words: Phonological Processor Processes speech sounds (phonemes)

Next is the orthographic processor, which is located in the occipital lobe in the lower back of the brain (Moats & Tolman, 2009). The orthographic processor allows us to recognize and recall the letters and letter sequences, or graphemes, of written words. Without it, we would be unable to make sense of printed text.

Illustration of the orthographic processor in the brain, with words: Orthographic Processor Recognizes letters and letter-patterns (graphemes)

Situated between the phonological and orthographic processors is an area called the “angular gyrus,” or, neurologically speaking, the temporal-parietal-occipital junction (Moats & Tolman, 2009). While this region of the brain is not a language processor in and of itself, it works alongside the orthographic and phonological processors, enabling us to associate spoken phonemes with the written graphemes that represent them. In the classroom, these associations should be taught and reinforced through explicit phonics instruction.

Illustration of the angular gyrus in the brain with words: Angular Gyrus Associates phonemes with corresponding graphemes

Our ability to recognize words is also facilitated by meaning and context processors, which are located in the temporal lobe of the brain (Moats & Tolman, 2009). The meaning, or semantic processor, allows us to interpret the meaning of words both in and out of context. Just because we can decode a word using our orthographic and phonological processors does not necessarily mean we can understand the word’s meaning. This principle is demonstrated by nonsense words, or sequences of letters that follow the spelling constraints of English but have no known meaning. For example, we can decode and pronounce nonsense words like "ip" and "glo" based on our knowledge of English spelling patterns. However, we cannot derive any meaning from them because we have not associated those letter patterns with any real-world concepts, as we have with patterns like “cat” or “pot.” The brain’s retention of a word’s meaning is tied to a number of features, including synonyms, spelling features, root words, related words, and more. 

The context processor works alongside the meaning processor to facilitate comprehension. Context can come in a variety of forms, including syntactic context, or the way a word is used grammatically, and content-based context, or the subject matter surrounding a given word. For example, syntactic context could help us differentiate between words like “duck” (noun) and “duck” (verb). In a sentence like “the duck swims in the pond,” our context processor would allow us to recognize that the word “duck” is being used as a noun, meaning it could not have the definition “to lower the head or body.” Content-based context would allow us to differentiate between words like “pool” (swimming) and “pool” (billiards). For example, in a sentence like “When it is hot out, I swim in the pool,” we can use the surrounding context to understand that the word “pool” here is referring to a body of water, not a game played with balls and cues.

All that said, it is important to note that context plays a limited role in word recognition. While it can support this process, it cannot replace the role of the phonological and orthographic processors, which are vital to fluent and accurate decoding.

Illustration of the meaning and context processors in the brain, with words: Meaning and Context Processors Allow us to interpret and remember what words mean in different contexts

Together, the four language processors—phonological, orthographic, meaning, and context—make up something called the “four-part processing model for word recognition.” This idea was first hypothesized in 1989 by researchers Mark Seidenberg and James McClelland and has since been referenced by numerous reading researchers (Seidenberg & McClelland, 1989). In this model, the phonological and orthographic processors work together to decode a written or spoken word. Then, the meaning and context processors work to attach meaning to the word that makes sense in context.

A graphic with four circles displayed in descending order from top to bottom, with the words: CONTEXT PROCESSOR MEANING PROCESSOR PHONOLOGICAL PROCESSOR ORTHOGRAPHIC PROCESSOR EXPLICIT  PHONICS INSTRUCTION Oral Language Output Oral Language Input Written

Notice that in this model, all four parts of the brain work together to support word recognition. This means that effective literacy instruction should engage all four processing systems and encourage them to be used in tandem.

One strategy that educators can use to ensure that all four processing systems are used during vocabulary learning is the POSSUM approach.

The POSSUM Approach

The POSSUM approach is a tool that educators can use to support explicit vocabulary instruction in the classroom. Dr. Maryanne Wolf is the author of this approach, which has been the basis for her evidence-based RAVE-O program in both its original and new iterations. The approach itself is based on two decades of cognitive neuroscience research on the developing reading brain (M. Wolf, personal communication, June 26, 2023). In this post, we will use the POSSUM acronym to describe six different elements of word recognition: phonology, orthography, syntax, semantics, understanding, and morphology. Engaging these six elements of word recognition during vocabulary instruction equips students to learn and retain new words. 


Phonology describes the sounds, or phonemes, that make up a word. As children develop phonological awareness, they learn how to pronounce unfamiliar words by breaking them down into their respective phonemes and blending those sounds together to produce a word. Not all students will innately understand how to segment a word, or break it into its individual phonemes. In fact, it is estimated that most children will need explicit instruction in phonological segmenting in order to successfully master the skill (Liberman & Shankweiler, 1985). 


Orthography describes the letters and letter sequences, or graphemes, that represent the sounds in a word. In order to read a word, students must be able to convert the graphemes they see into phonemes that they can pronounce. In order to spell a word, students must convert the phonemes they hear into graphemes that they can write down. Sometimes, graphemes are made up of more than one letter. For example, in the word “trash,” the /sh/ sound is represented by two letters. When two adjacent letters combine to represent one speech sound, the resulting sound is called a “digraph.” Graphemes can also be made of three adjacent letters, which is called a “trigraph,” or four adjacent letters, which is called a “quadrigraph.” Graphemes that are made up of more than one letter can be difficult to decode. Students should be explicitly taught different syllable types and spelling rules to reinforce their understanding of these words. The six major syllable types are: closed, open, r-controlled, vowel team, silent -e, and consonant -le. Note: Some educational materials categorize diphthongs as separate from vowel teams, resulting in seven major syllable types. The same principles of explicit instruction still apply. For more information on each syllable type, see our Reading Glossary.


Syntax describes how a word functions grammatically within a sentence. In order to understand words syntactically, students must receive explicit instruction in the different parts of speech and how to recognize them. For example, understanding that the word “child” is a noun and that nouns generally precede verbs in English sentences would be a type of syntactic knowledge.


Semantics describes an understanding of what a word means. This includes both the word’s definition in context, as well as other meanings the word can have. Students with a high semantic knowledge have a large and nuanced vocabulary.


Students may also use background knowledge from outside the text to understand a word. For example, they may have seen the word before in another context, or they may be able to associate the word with something they are exposed to in their daily lives.


Morphology describes all of the parts that make up a word, including prefixes (“un-,” “re-,” “anti-“), suffixes (“-ly,” “-acy,” “-able”), and root words (“astro,” “script,” “phobia”). An understanding of a word’s etymology—the origin of the word and how its meaning has changed over time—can be helpful when dissecting its morphology.

Practical Application

Educators can implement POSSUM when teaching new vocabulary words in the classroom. Students may benefit from the use of graphic organizers, such as our downloadable POSSUM Graphic Organizer (see "Supplemental Resources for Teachers and Families"), to keep track of new vocabulary terms. Caregivers can also use the POSSUM Graphic Organizer with their child when reading at home. Here are two examples of how the six elements of POSSUM can be used to support the learning of both simple and complex words. Note: strategies and applications may vary slightly from program to program.

Example 1

Core Word


Example Sentence

“Melissa told her friend to sit down and stop talking.”


Review sounds: /s/ /t/ /o/ /p/


Review spelling: s-t-o-p

Syllable types: closed syllable

Spelling rules: short-vowel rule


Parts of speech:

  • Noun → “Soon, the music came to a stop.”
  • Verb → “Please stop bothering me.” (used in the example sentence)
  • Adjective → “She hit the stop button to pause the movie.”


Possible meanings:

  • Stop (noun): a pause or breaking off; something that impedes or obstructs
  • Stop (verb): to get in the way of; to cease or quit (used in the example sentence)
  • Stop (adjective): designed to stop


Use background knowledge to make connections:

  • Have I seen or heard this word used elsewhere?
    • “stop sign”
    • “stop, drop, and roll”
    • “to put a stop to”


Explore word parts: n/a

Additional conjugations:

  • stopped → past tense verb
  • stops → present tense verb
  • stopping → present progressive verb

Example 2

Core Word


Example Sentence

“Her friend’s reply was practically inaudible.”


Review sounds: /i/ /n/ /au/ /d/ /i/ /b/ /l/


Review spelling: i-n-a-u-d-i-b-l-e

Syllable types: closed syllable, vowel team, open syllable (schwa), consonant -le

Spelling rules: “au” makes the “aw” sound, open “i” with schwa pronunciation, -le syllables always end in silent “e”


Parts of speech:

  • Adjective → “Her words were inaudible through the glass.”


Possible meanings:

  • Inaudible (adjective): unable to be heard


Use background knowledge to make connections:

  • Have I seen or heard this word used elsewhere?
  • Have I seen or heard parts of this word used elsewhere?
    • “in”
      • “indirect”
      • “inexpensive”
    • “audi”
      • “audio”
      • “audience”
    • “ible”
      • “accessible”
      • “visible”


Explore word parts:

  • Prefix: in → not
  • Root word: audi → to hear
  • Suffix: ible → to be capable of

Additional conjugations:

  • inaudibly → adverb

Why It Works

Breaking down unfamiliar words using the POSSUM approach equips students to learn and retain new vocabulary terms. As we saw above, the brain’s ability to recognize words relies on several different systems and requires phonological, orthographic, semantic, and contextual input. The reason the POSSUM approach works is that it encourages educators to explicitly teach new vocabulary in a way that systematically engages all four systems of language processing. Because these areas are interconnected and interrelated, activating them at the same time can lead to a ripple effect of literacy benefits.

For example, it has been demonstrated that explicit instruction in morphology can lead to increased proficiency in grapheme-phoneme mapping, as it provides an additional connection in the brain that supports rapid word recognition and comprehension (Bowers et al., 2010). When students receive explicit instruction in phoneme-grapheme relationships, as well as the ways in which morphology, syntax, and other variables can affect these relationships, they are also better equipped to become proficient spellers than if they are taught to spell through memorization alone (Ball & Blachman, 1991; Berninger et al., 2002). A greater awareness of orthography, or spelling, can in turn increase the depth of students’ vocabulary, as well as their reading and writing proficiency (Graham, 2000; Graham et al., 2018). For example, a student who has been taught that the root “geo-” in the word “geography” means “earth” may be able to apply this knowledge to understand other words, like “geology” or “geocentric.”

Additionally, studies have shown that curricula that use the POSSUM approach have more significant effects on students’ reading fluency and comprehension than those that use only isolated phonics instruction or repeated reading (Morris et al., 2011; Lovett et al., 2017). While POSSUM originates from the RAVE-O curriculum, this evidence-based approach can be integrated into any classroom as a way of providing systematic and explicit vocabulary instruction.


The number of words in the English language is almost incalculable. There are around 600,000 words listed in the Oxford English Dictionary alone. Developing a thorough and useable understanding of these words through memorization and context clues alone would be an impossible task. However, when vocabulary learning is supported by a systematic approach, such as POSSUM, and also paired with explicit instruction in decoding and language comprehension skills, guesswork and memorization are taken out of the equation. Instead, students are taught the practical knowledge they need to break down new and unfamiliar words, taking their literacy skills to new heights.

Supplemental Resources for Teachers and Families

POSSUM Graphic Organizer

Educators can use this graphic organizer in the classroom to structure vocabulary learning and help students work through all six elements of the POSSUM approach. Caregivers may also use this resource to support vocabulary learning while reading with their children at home.

Breaking Down New Words Worksheet

Studying new words through the elements of the POSSUM acronym—phonology, orthography, syntax, semantics, understanding, and morphology—helps learners solidify their mental representations of the words. Using this worksheet, teachers can guide students through the process of analyzing words through each of these lenses.


Ball, E. W., & Blachman, B. A. (1991). Does phoneme awareness training in kindergarten make a difference in early word recognition and developmental spelling? Reading Research Quarterly26, 49–66.   

Berninger, V. W., Vaughan, K., Abbott, R. D., Begay, K., Coleman, K. B., Curtin, G., . . . Graham, S. (2002). Teaching spelling and composition alone and together: Implications for the simple view of writing. Journal of Educational Psychology94, 291–304.

Bowers, P. N., Kirby, J. R., & Deacon, H. S. (2010). The effects of morphological instruction on literacy skills: A systematic review of the literature. Review of Educational Research80, 144–179.

Gough, P. B., Alford, J. A. Jnr., & Holley-Wilcox, P. (1981). Words and contexts. In O. J. L. Tzeng and H. Singer (eds.). Perception of print: Reading research in experimental psychology. Erlbaum Associates.

Graham, S. (2000). Should the natural learning approach replace spelling instruction? Journal of Educational Psychology, 92, 235–247.

Graham, S., Harris, K. R., & Adkins, M. (2018). The impact of supplemental handwriting and spelling instruction with first grade students who do not acquire transcription skills as rapidly as peers: A randomized control trial. Reading and Writing: An Interdisciplinary Journal31, 1273–1294.

Liberman, I., & Shankweiler, D. (1985). Phonology and the problems of learning to read and write. Remedial and Special Education6(6), 8–17.

Lovett, M. W., Frijters, J. C., Wolf, M., Steinbach, K. A., Sevcik, R. A., & Morris, R. D. (2017). Early intervention for children at risk for reading disabilities: The impact of grade at intervention and individual differences on intervention outcomes. Journal of Educational Psychology10, 889–914.

Moats, L. & Tolman, C. (2009). Language essentials for teachers of reading and spelling (LETRS): The challenge of learning to read (Module 1, 2nd e.d.). Sopris West.

Morris, R. D., Lovett, M. W., Wolf, M., Sevick, R. A., Steinbach, K. A., Fritjers, J. C., & Shapiro, M. (2011). Multiple-component remediation for developmental reading disabilities: IQ, SES, and Race as factors on remedial outcome. Journal of Learning Disabilities45, 99–127.

Seidenberg, M. S. & McClelland, J. L. (1989). A distributed, developmental model of word recognition and naming. Psychological Review96, 523–568.

Stanovich, K. E. (1980). Toward an interactive-compensatory model of individual differences in the development of reading fluency. Reading Research Quarterly, 15(1).


Editor's Note: This post was edited on June 26, 2023 to clarify that Dr. Maryanne Wolf is the author of the original POSSUM framework.