Teaching Vocabulary Is More Than Memorizing Definitions: What Parents Should Know
When a child struggles with reading comprehension, it can be tempting to focus primarily on reading the words correctly or answering questions after a passage. But there is another piece of the puzzle that matters tremendously: vocabulary.
If a child can read a sentence but does not understand the meaning of several important words in that sentence, understanding the bigger message becomes much harder.
A 2026 study by Harker and Stevenson looked specifically at vocabulary instruction for third-grade students with language learning disorders (LLDs), including students with speech-language impairment and specific learning disabilities in reading.
The findings reinforce something I talk about frequently with families: we cannot assume that simply hearing, reading, or looking up a new word means a child has truly learned it.
Why Vocabulary Can Be Hard for Children With Language and Reading Difficulties
Learning a new word is actually a pretty complex language task.
A child has to hear and process the sounds in the word, remember its pronunciation, understand its meaning, connect it to things they already know, recognize it when they hear or read it again, and eventually retrieve and use it independently.
Children with language learning disorders may have difficulty with several pieces of this process. They may struggle to process and store the sounds within words, understand definitions, connect new vocabulary to existing semantic knowledge, or understand subtle differences between related words. Background knowledge, executive functioning, and inferencing abilities can also affect vocabulary learning.
In other words, these children absolutely can learn new vocabulary—but they may need vocabulary to be taught much more explicitly and repeatedly.
So, What Does Good Vocabulary Instruction Look Like?
The researchers used what is called rich vocabulary instruction.
Rather than asking children to memorize a dictionary definition, effective vocabulary teaching involves helping children build a deeper understanding of the word. This can include child-friendly definitions, repeated exposure to the word, paraphrasing meanings, and discussing examples and nonexamples.
In this study, the intervention went even further. Students worked on five words at a time, twice per week. Instruction incorporated phonological awareness, morphological awareness, pictures, definitions, student-created flashcards, and opportunities to quiz one another. The second session provided another explicit review of those same words.
For an SLP, reading specialist, teacher, or parent, that might look something like this:
Say it: What sounds and syllables are in the word?
Define it: Explain the word in child-friendly language.
Connect it: What other words or ideas does it remind us of?
Break it apart: Does it contain a prefix, suffix, or root that gives us a clue?
Visualize it: Draw it, act it out, or create a mental picture.
Use it: Put the word into different sentences and situations.
Compare it: Discuss examples, nonexamples, synonyms, antonyms, and related words.
Come back to it: Revisit the word again later rather than teaching it once and moving on.
Did It Work?
For learning the vocabulary words themselves, yes.
During the treatment phase, the students' average vocabulary score increased from 0.69 before instruction to 5.09 after instruction on a 9-point measure. The researchers found a moderate overall treatment effect on vocabulary learning.
Across the 25 words taught during intervention, students mastered an average of 17 words, or 68%, immediately after instruction.
That is an important finding. Children with language-based learning difficulties can make meaningful vocabulary gains when words are taught explicitly and intentionally.
But there was another important finding.
Knowing More Words Did Not Automatically Improve Reading Comprehension
The researchers did not find a treatment effect on passage comprehension.
That doesn't mean vocabulary instruction isn't important for comprehension. Instead, it highlights something parents often hear me say:
Reading comprehension is not one skill.
Knowing the meanings of words is essential, but understanding a text also requires children to connect ideas, understand sentence structures, make inferences, activate background knowledge, monitor whether something makes sense, and integrate information across a passage.
Teaching a child the word reluctant, for example, is valuable. But knowing the definition of reluctant does not automatically mean the child can understand why a character behaved reluctantly, connect that behavior to earlier events, infer the character's feelings, and explain the author's message.
Vocabulary is part of the comprehension puzzle—not the entire puzzle.
The Other Big Takeaway: Repetition Matters
Perhaps one of the most practical findings for parents is what happened after instruction stopped.
After a month without treatment, students remembered some of what they had learned, but their vocabulary scores decreased substantially compared with their immediate posttest performance.
Interestingly, students had been exposed to the target words many times during the intervention, yet their vocabulary scores still declined during the maintenance period. This highlights the potential importance of spaced practice—revisiting words across days and weeks rather than concentrating all of the practice into a short period.
For children with language disorders, "we already taught that word" may not be enough.
We need to come back to it.
And then come back to it again.
What This Means for Parents
If your child has dyslexia, developmental language disorder, another language-based learning disability, or persistent reading comprehension difficulties, vocabulary instruction should go beyond vocabulary lists and weekly quizzes.
The goal isn't simply:
"Can you tell me the definition?"
We want to know:
"Do you really know this word?"
Can your child recognize it? Explain it in their own words? Use it in a sentence? Connect it to another word? Understand it when it appears in a different context? Recognize its meaningful word parts? Retrieve it a week later?
That deeper knowledge is what helps vocabulary become part of a child's language system.
Where Speech-Language Pathologists Fit In
Vocabulary sits directly at the intersection of language and literacy, which is why SLPs can play such an important role for children with reading and language difficulties.
We can work beyond memorizing isolated definitions by helping children understand how words sound, what they mean, how they are built, how they relate to other words, and how they function within sentences and texts.
For a child struggling with reading comprehension, sometimes the question shouldn't only be:
"Can they read the words?"
It should also be:
"Do they understand the language behind the words?"
And that distinction can make a big difference in determining the kind of support a child actually needs.
Reference
Harker, B., & Stevenson, N. A. (2026). Vocabulary instruction for children with language learning disorders: Effects on word learning and comprehension. Language, Speech, and Hearing Services in Schools, 57, 674–692.