While it has been argued that a relatively small number of words make up half of what is written in English, it is the resulting 50 per cent that carry most of the meaning in a written text. It is hardly surprising, then, that a student's ability to comprehend what is read is dependent on their vocabulary knowledge. In seminal research by Cunningham and Stanovich (1997), the vocabulary size of students in first grade strongly predicted reading comprehension in eleventh grade (Year 11). This relationship between vocabulary and comprehension has been further substantiated in more recent literature. There is corresponding research to suggest that students who begin school with a poor vocabulary demonstrate 'lexical processing problems' and are at risk of reading failure and overall academic underachievement. It has also been argued elsewhere that vocabulary knowledge is necessary for decoding and fluency. Writing is also impacted by vocabulary.
According to Dobbs and Kearns (2016) strong language skills help a writer to manage the cognitive complexities associated with writing. Furthermore, the difference between the vocabulary knowledge of children from high and low socioeconomic backgrounds has been well documented, making the teaching of vocabulary an equity issue, deserving of a place of priority in the classroom teaching and learning program. Throughout this chapter, we will explore this topic in a range of ways, including some discussion of the kinds of words to teach and how to teach them.