Derivation applies to the stem-forms of words, without their inflectional endings, and creates new, more complex stems to which inflectional rules can be applied (The Grammar of Words, 2012)。 In morphology, derivation is an affixation process that forms a word with a meaning or category distinct from that of its bases。 Usually, derivational affixes can be pided in to two categories: suffixes e。g。 –able and prefixes e。g。 dis–。 Sometimes, derivation can be applied more than once。 For example: unemployment can be pided into prefix “un-”, stem “employ” and suffix “-ment”。

1。3 Introduction of Second Language Learning

Second language learning (SLL) is concerned with the process and study of how people acquire a second language, which is often referred to as L2 or target language, as opposed to L1 (the native language)（Dr。 Angelika Rieder-Bünemann,2012）。 Second language can be any language in addition to the native language。 In this study, second language specifically refers to English。 

Because of the learning habits of inpidual’s native language, L2 learning is always an arduous task for L2 learners: For example, in Chinese, compounding words take the majority part of the word formation。 While in English, derivational word occupies an important place in word formation, so compare to the compounding rules, it is rather difficult for a Chinese learner to master the derivational rules。 Thus solving this kind of bilingual problem, L2 Learning will no longer be a difficult task。

2。 Literature Review

2。1 English lexicology and Second language learning

In the master thesis “The current situation of English lexicology teaching and learning”，Qiao (2011) claims that English lexicology offers students insight into the origin and development of the English vocabulary．It deals with meanings of modem English words and their changes in the course of historical development．It discusses the problems of word structure and word formation in English，including the formation of new words which have appeared since the 1960s．It also studies the use of English words，phrases and idioms．In this term，the significance of English lexicology for language learning is evident．

2。2 Language proficiency and its influence on WDK acquisition

Whether the English proficiency had an influence on WDK acquisition is a controversial topic。

Here is the essence of the published debate: Wu Xudong&ChenXiaoqing’s (2000) study indicated that student’s knowledge is effected by the L2 proficiency, the higher student’s L2 level is, the more their affix knowledge will be。 In addition, it's worth noting that when L2 Level achieves a Medium level, the speed of affix knowledge acquisition will slow down apparently。 Next, WU Keyan(2008) pointed out that a profound study will help L2 Learners to apply suffix derivative sand thus will be beneficial to bettering the expression effect, to enhancing the L2 Learners’ productive vocabulary ability and English expressing ability and to do a good job in translation。 Also, QianJingjing(2011) claimed in her paper that student’s affix acquisition is influenced by the English proficiency。 With the enhancement of second language proficiency, student’s affix knowledge will have a corresponding increase。

In addition, Maria Singson, Diana Mahony and Virginia Mann (2000) claimed in their paper“The relation between reading ability and morphological skills: Evidence from derivational suffixes”that knowledge of derivational suffixes increases with grade level, along with decoding ability and phoneme awareness。 Leontjev (2016) did a study to examine whether Bauer and Nation’s (1993) teaching order of L2 English affixes can account for the difficulty learners have with recognizing the affixes。 The participants in the study were L1 Estonian and Russian learners of English at upper secondary schools in Estonia。 Their performance was measured on a word segmentation task。 There were significant differences in the number of affixes the learners were able to successfully recognize at different levels, as classified by Bauer and Nation (1993)。 By and large, with the exception of no significant difference between Level 5 and Level 6 affixes, the higher the affix level was, the less likely the learners were to recognize the affixes at this level。