1. Defining key terms

Lexical richness： Lexical richness is widely assumed to be an important part of lexical proficiency. In some studies lexical richness is considered an umbrella term， covering different dimensions of lexical competence， such as lexical diversity， lexical sophistication， lexical density and lexical accuracy （Read 153）. Also， lexical richness can be illustrated by frequency-based definition. It is assumed that low-level learners will have access to high-frequency words， whereas a high proportion of low frequency words is supposed to indicate an advanced level of vocabulary knowledge （Ineke Vedder amp; Veronica Benigno 25）. Lexical richness measures are used to evaluate the lexical proficiency level of a child or student， comparing their lexical richness with an external reference point（Azodi， Karimi amp; Vaezi 1839）.

2. Data collection and analysis

The data on which the analyses were conducted were consisted of short argumentative essays written by two college students， of which one majors in English and the other majors in Chinese. Two writing tasks were assigned to the students and they are asked to work out a text of at least 250 words within 35 minutes . The two tasks were similar in terms of task type， structure and topic. When finishing collecting the writings， I put them into the Corpus and analyze the lexical richness of the two writings in the aspects of word frequency and word accuracy.

3. Results and discussion

3.1 Word frequency

As shown by Table 1， the results for both tasks are fairly similar. The proportion of high frequency words is highest in both two passage while the low frequency words consist the lowest proportion. The percentage of high frequency words is much higher in passage 2 （77%） than in passage 1 （68%）. However， the proportion of low frequency words is slightly low in passage 1 （10%） than in passage 2 （12%）.

As can be deduced from Table 1， there are several differences in lexical richness between the English major and non-English major students. The non-English major student uses more high frequency words than the English major student， which shows that when they think of the words to express their opinions， the words they choose are always the same and the easier ones. With respect to the middle frequency words， the proportion in the writing of non-English major student is as low as that of low frequency words， whereas the proportion in English major student’s writing is as much as twice than that of low frequency words. We can say that as for the non-English major students， the words they choose are of two sides， either the most common ones or sometimes the sophisticated ones. That’s possibly because the middle frequency words need more practice than low frequency words， and the non-English major students have less time and opportunities to use those words. Also， the amount of written input learners receive varies according to their field of study.（Laufer amp; Nation 25）. With regard to the use of low frequency words， the percentage in passage 2 has a tiny advantage than passage 1. In order to see clearly the content of the words in low frequency， I make up the Table 2.

According to Table 2， the type of part of speech in the list of the low frequency words is similar both in passage 1 and 2. They are adjectives， nouns， verbs and adverbs. Overall， the adjectives and nouns consist most of the low frequency words. However， in passage 1， the numbers of nouns and adverbs are much bigger than in passage 2 while the numbers of adjectives and verbs are the opposite. Table 2 tells us that non-English major students use more sophisticated adjectives and verbs， and English major students use more nouns and adverbs of low frequency.

3.2 Word accuracy

From Table 3， we can get the information about word accuracy in both passages. I picked up three words in each passage randomly from high frequency to low frequency， and to compare the collocations in the text with those in the corpus. If the collocation is shown as the recommended list， I will highlight the words， and if not， I try to find the collocation in the lists below. According to Table 3， English major students can use the correct phrase of all word frequencies （though the phrase of high frequency is not so common used）. However， the non-English major student made a mistake in using the low frequency word--- the phrase he used doesn’t appear in the list. It indicates that though the non-English major students can also use as many low frequency words as English major students， their accuracy can not be assured.

3.3 Discussion

The findings of this study can be useful in the field of language pedagogy. We’ve concluded that the non-English major students use much more high frequency words than English major students， but they will make mistakes in the use of low frequency words. Nation （Teaching Vocabulary） believes teaching can effectively deal with only a small amount of information about a word at a time. The more complex the information is， the more likely the learners are to misinterpret it. As a result， teachers should select the teaching materials intensively， and make sure that the materials have the necessary lexical items for the learners which include high frequency words， low frequency words， and academic words（Meara， 27）. Meanwhile， the criterion of the materials in terms of the lexical items should be different for non-English majors and English majors.

Works cited：

Azodi， Karimi amp; Vaezi. “Measuring the lexical richness of productive vocabulary in

Iranian EFL University students’ writing performance”. Theory and Practice in

Language Studies， Vol. 4， No. 9， （2014.9）， 1837-1849

Ineke Vedder amp; Veronica Benigno. “Lexical richness and collocational

competence in second-language writing. “ De Gruyter Mouton （2016）; 54（1）;

23-42.

Laufer amp; Nation. “Passive vocabulary size and speed of meaning recognition.”

EUROSLA Yearbook 1（2001）， 7-28.

Meara. “Lexical Frequency Profiles： A Monte Carlo Analysis.” Applied Linguistics

（2005）， 26 （1）， 32-47.

Nation. “Teaching Vocabulary. “ The Asian EFL Journal， 7（3）， （2005）， 47-54.

Read. Assessing vocabulary.Cambridge： Cambridge University Press， 2000.