For children to meaningfully increase their knowledge of vocabulary, direct instruction is essential. Research shows that reading alone is not enough.
Missed opportunities for vocabulary learning
Nearly everything that a child needs to know in order to flourish academically can be found in books – reading is absolutely the key to knowledge. This is very true, except that children can’t learn what they don’t understand. A research study reports that children deem a text too difficult when they don't know at least 98% of the vocabulary in it. And how much can we rely on the expectation that they will figure out the meaning of unfamiliar words based on the context? According to research, not too much.
A study by Swanborn and de Glopper (1999) found that left to read alone, the average child will spontaneously ‘work out’ the meanings of only 15% of the unfamiliar words they encounter. To put this into perspective, a study by Carver (1994) found that in a typical 12,000 word children’s book, there will be 240 new words, of which an unsupported child will learn just 36 at the first time of reading. The rest will remain a mystery, limiting that child’s understanding and enjoyment of the story.
On the contrary, if children are given definitions of tricky words they encounter, the percentage of new words being understood and learned could increase from 15% to 37% . This suggests that additional information about unfamiliar words can really make a difference and reveals the vital need for direct vocabulary instruction.
Vital need for direct vocabulary instruction
Numerous experts have pointed to the vital need for direct vocabulary instruction both at school and at home. As Andrew Biemiller suggests, the two central pillars to literacy learning are phonics and vocabulary – and although phonics has generally received enough attention, vocabulary has been left behind. The consequence of this is that many children are capable of “sounding out” the new words they come across, but are much less prepared to understand them. The trap is that once children have developed the ability to convert the letters on a page into recognisable words, they are suddenly deemed to be competent readers despite no clear teaching of what words actually mean. This is why phonics and vocabulary instruction should be taught together!
Thankfully, policy makers are beginning to take notice of this discrepancy. In the UK, in an action plan outlined in December 2017, the British government committed to improving vocabulary learning, acknowledging its status as a “fundamental building block of literacy”. The report pointed to the cross-curricular benefits of improving vocabulary, noting that children who experience early language difficulties are six times less likely to reach the expected level in English by age 11 and even less likely to achieve the minimum standard in maths.
Similarly, according to the US Common Core Standards, “The importance of students acquiring a rich and varied vocabulary cannot be overstated.” The document reports that the difference in students’ vocabulary levels is largely responsible for the gap in their academic achievement, yet, vocabulary has not been taught frequently nor systematically in schools. The Standards recommend incremental, repeated exposure to words in a variety of contexts that would enable children to adequately grasp the whole range of the meaning that words have.
Overall, converging research evidence supports that explicit vocabulary instruction yields significantly better results than reading alone., , 
Complement your child’s reading with focused vocabulary guidance
Explicit vocabulary instruction means providing children with rich content about words, such as definitions, synonyms and antonyms, and information about how the word is used in different contexts. It means talking about and interacting with words. This active engagement with words enhances learning and memorisation much more effectively than incidental and passive word learning. It also builds what literacy experts call word consciousness, that is, awareness of how language works and how to interact with it. Word consciousness helps children use the new words they acquire successfully and it increases the chances of them inferring the meaning of unfamiliar words by themselves.
In fact, research suggests that up to the age of ten, 80% of words children learn are acquired as a result of direct explanation, rather than just ‘figuring it out’ while reading. For parents, care-givers, and teachers, this means taking advantage of any opportunity to introduce children to new vocabulary, ask questions, and talk about the words!References
 Anderson, R., & Freebody, P. (1981). Vocabulary knowledge. In. J. Guthrie (Ed.). Comprehension and teaching: Research reviews. Newark, DE: International Reading Association. 77-117.
 Swanborn, M.S.L. and de Glopper, K. (1999) Incidental Word Learning while Reading: A Meta-Analysis. Review of Educational Research. 69: 261-85.
 Carver, R. (1994). Percentage of unknown vocabulary words in text as a function of the relative difficulty of the text: implications for instruction. Journal of Reading Behavior. 26: 413-437.
 Biemiller, A. and Boote, C. (2006) An Effective Method for Building Meaning Vocabulary in Primary Grades. Journal of Educational Psychology. 98: 44-62.
 Biemiller, A. (2001) Teaching Vocabulary: Early, Direct, and Sequential. American Educator. 25: 24-28.
 United Kingdom, Department for Education (2017) Unlocking Talent, Fulfilling Potential: A plan for improving social mobility through education. UK: APS Group. Common Core State Standards for English Language Arts & Literacy in History/Social Studies, Science, and Technical Subjects. Appendix A: Research Supporting Key Elements of the Standards.
 Beck, I., McKeown, M. (2007). Increasing Young Low-Income Children’s Oral Vocabulary Repertoires through Rich and Focused Instruction. The Elementary School Journal, 107: 251-271.
 Marulis, L., & Neuman, S. (2010). The Effects of Vocabulary Intervention on Young Children's Word Learning: A Meta-Analysis. Review of Educational Research, 80: 300-335.
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: 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: 391-410.
 Beck, I., McKeown, M. and Kucan, L. (2002) Bringing words to life: Robust vocabulary instruction. New York: Guildford Press.