As we saw in Chapter 1, children learn thousands their first language with little observable effort. The task of acquiring a large vocabulary is quite different for second language learners. For one thing, they are likely to be exposed to far smaller samples of the language to be learned. Also, the contexts in which second language learners encounter new vocabulary may not be as helpful as those in which children learn the first one or two thou sand words of their first language. If they are older children or adults, the words they are exposed to may be more difficult, referring to meanings that are not easily guessed from context. Marcella Hu and Paul Nation(2000) showed that, in order to understand a text without frequent stops to consult a dictionary, one needs to know more than 95 per cent of the words a rare case for second language learners at most stages of acquisition. Although the two or three thousand most frequent words in English make up as much as 80-90 per cent of most non-technical texts, less frequent words are crucial to the meaning of many things we hear and read. For example, the meaning of a newspaper article about a court case may be lost without the knowledge of words such as testimony, 'alleged', or 'accomplice'.