Explanations and Definitions

The intention in this chapter is to give working explanations of vocabulary and the various ways it can be measured. The chapter will not discuss every option and detail about why these measures have evolved exactly as they have, but should provide readers with an understanding of the terms used in this book. It will cover:

• What is vocabulary and what is meant by a word?

• What is word knowledge?

• How can vocabulary knowledge be measured?

We live in a society where we measure things all the time: our height, our weight, our shoe size, our car speed. We do it automatically and rarely think about the units we use for measurement until, that is, the units change for some reason. For example, exactly how fast is the maximum speed limit of 120 kph on roads in continental Europe when your car (my car, at least, it's an old one) only gives miles per hour (mph) on the speedometer? In order to measure anything, therefore, we need to understand the units of measurement and use them appropriately. Measuring language, and vocabulary knowledge in particular, is no exception. Misunderstand the units, or use the wrong units, and we are likely to learn very little about the language we are trying to understand. The purpose of this opening chapter is to explain what these units of measurement are in describing vocabulary acquisition and how we set about measuring vocabulary knowledge.

Measuring language is not as easy as measuring distance or weight. Language knowledge is not a directly accessible quality and we rely on learners to display their knowledge in some way so it can be measured. If learners are tired or uninterested, or misunderstand what they are expected to do, or if we construct a test badly, then they may produce language that does not represent their knowledge. A further problem arises with the qualities of language we are interested in monitoring. Grammar, for example, does not come in conveniently sized packages that can be counted. The techniques we frequently use to elicit language from learners, such as writing an essay, provide data that are not easy to assess objectively. We tend to grade performance rather than measure it and this can lead to misinterpretation. For example, if two essays are given a mark out of 10, and one is given 8 and the other 4, this does not mean that the first learner has twice the knowledge or ability as the second, even though the mark is twice as large. The use of numbers for grading suggests this ought to be the case, but it is not so. In these circumstances, it is hard to characterise second language knowledge and progress accurately or with any precision; it is hard to measure language. One of the advantages of examining vocabulary learning in a second language is that, superficially at least, it is a quality that appears to be countable or measurable in some meaningful sense. You can count the words in a passage or estimate the number of words a learner knows, and the numbers that emerge have rather more meaning than a mark out of 10 for an essay. A passage of 400 words is twice as long as a passage of 200 words. A learner who knows 2000 words in a foreign language can be said to have twice the knowledge of a learner who knows only 1000 words. While the principle of this looks very hopeful, in reality, assessing vocabulary knowledge is not quite so easy. It is not always clear, for example, exactly what is a word, and what appears to be a simple task of counting the number of words in a text can result in several possible answers. Again, in estimating the number of words a learner knows, it is possible to come up with several definitions of knowledge, some more demanding than others, which might produce very differently sized estimates. The following sections will explain the terms that are used in measuring vocabulary knowledge and learning, and will set some ground rules for the terms used in this book.

What is Vocabulary and What is Meant by a Word?

One thing the reader will find in accessing the literature on vocabulary knowledge, is that we tend to use the word 'word', presumably for ease and convenience, when we are really referring to some very specialist definitions of the term, such as types, tokens, lemmas, word families and even the attractively named hapax legomena. This can be very confusing, even depressing. My undergraduate students, for example, having read that native speakers of English know something like 200,000 words (Seashore & Eckerson, 1940), are mortified to find that their vocabularies appear less than one tenth of this size when they try out Goulden et al.'s (1990) or Diack's (1975) vocabulary size tests. The reason is that early estimates of the vocabulary knowledge of native speakers, such as Seashore and Eckerson's, used a dictionary count where every different form of a word included in the dictionary, was counted as a different word. Words such as know, knows and knowing were all treated as different words and counted separately. Later attempts to systematise such counts and use frequency information for greater accuracy, such as that of Goulden et al., include a treatment of all the common inflections and derived forms of words as a single word family. By this method, know, knows and knowing and many other similar forms are all treated as a single unit. Not surprisingly, this method of counting comes up with a smaller count than Seashore and Eckerson's — but often the result is still called a word count.

So, what is a word and how do we count it? In one sense, it can be very simple. Faced with a sentence like,

The boy stood on the burning deck,

we can count up the number of separate words in the sentence. In this case, there are seven separate words. This type of definition is useful if we want to know how many words there are in a passage, for example, or how long a student's essay is. It is also the type of definition used by dictionary compilers and publishers to explain how big the corpus is, which they use to find real examples of word use. When counting words this way, words are often called tokens to make it quite clear what is being talked about. So, we would say that the example sentence above contains seven tokens.

Sometimes you will see the expression running words used with much the same meaning. Where dictionaries give information about how frequent a word or expression is, you may be told that a word occurs once every so many thousand or million words or running words. The most common words in languages are much more frequent than this. In English, the three most...