There's generally a direct relationship between reading and vocabulary in that children who read a lot have more opportunities to come across new vocabulary, and children who have a broader vocabulary are more willing to engage often with more complex texts which, in turn, expose them to further vocabulary.
But what happens in the case of children with dyslexia for whom reading can be challenging and, as such, it is less available as a means of vocabulary development? Fortunately, the difficulty these children have with reading doesn’t mean that they are doomed to suffer from an impoverished vocabulary; all it means is that explicit vocabulary guidance is even more crucial for them than it is for children without dyslexia.
Explicit vocabulary guidance means giving children enough information around each new word they are learning, such as child-friendly definitions, example sentences, rich context, and activities that promote a deeper and more accurate comprehension of the meaning of the new word. Converging research evidence shows that this method generally yields significantly better results than reading alone , . But there’s experimental evidence indicating that explicit vocabulary teaching is particularly effective for children with dyslexia.
One of the benefits of explicit instruction is that it gives children the opportunity to associate a word with rich enough information to comprehend what it means deeply and accurately. It also increases word consciousness which means that children become more aware of relationships between words, how language works in general and how to interact with it. Children who build word consciousness gradually become more competent at inferring the meaning of unknown words by themselves.
Of course, comprehending the meaning of a new word is only part of the story; in order for the acquisition of a new word to be completed, children also need to be able to remember it. This can be another challenge for children with dyslexia due to the working-memory limitations they often suffer from. Exactly because they find it difficult to keep a large amount of information in their working memory, this information is less likely to make it to their long-term memory. Thus, even though effective educational methods should always work on both learning and remembering newly acquired words, for children with dyslexia the emphasis on remembering them is even more crucial.
This is exactly what explicit vocabulary guidance does: it provides rich content that engages children’s attention and requires their active participation in ways that enhance learning and retention of new words much more effectively than incidental, passive word learning.
 Biemiller, A. and Boote, C. (2006) An Effective Method for Building Meaning Vocabulary in Primary Grades. Journal of Educational Psychology, 98, 44-62.
 Marulis, L., & Neuman, S. (2010). The Effects of Vocabulary Intervention on Young Children’s Word Learning: A Meta-Analysis. Review of Educational Research, 80(3), 300-335.
 Reiss, E. (2010). Evaluating the effectiveness of a tier 2 vocabulary intervention on the writing and spelling of elementary students with dyslexia: A formative case study (MA Thesis. University of Toronto).
 Coyne, M., McCoach, B., Loftus, S., Zipoli Jr., R., Ruby, M., Crevecoeur, Y., & Kapp, S. (2010) Direct and Extended Vocabulary Instruction in Kindergarten: Investigating Transfer Effects. Journal of Research on Educational Effectiveness 3(2), 93-120.
 Loftus-Rattan, S., Mitchell, A. (2016). Direct Vocabulary Instruction in Preschool: A Comparison of Extended Instruction, Embedded Instruction, and Incidental Exposure. The Elementary School Journal. 116(3), 391-410.