Initially, Rubin (1975) came up with a general definition: “the techniques or devices which a learner may use to acquire knowledge” (P43)。 Later, Bialystok (1978) regarded learning strategies as “optional means for exploiting available information to improve competence in a second language” (P71)。 As for Weinstein & Mayer (1986), they expanded the definition, asserting that learning strategies not only facilitate our cognition area: “in which the learner selects, acquires, organizes, or integrates new knowledge” (P315) but also are used for affecting our motivational or affective status, thus benefiting language acquisition。 Similarly, in the introduction of Chamot & O’Malley (1990) of their book, they put an idea like Weinstein and Mayer that learning strategies are specific actions or thoughts taken by learners to deepen their comprehension, learning and memory of new information。

One of the mostly well-recognized theories is written by Oxford(1990), in which she put forward her understanding: “learning strategies are specific actions taken by the learners to make learning easier, faster, more enjoyable, more self-directed, more effective and more transferable to new situations”(P8)。 And later Oxford & Cohen (1991) provided a comprehensive review about learning strategies。 As what they have collected from previous studies, for improving their language skills, learners conduct the methods—learning strategies, which are effective in: “increase attention essential for learning a language; enhance rehearsal that allows linkages to be strongly forged; improve the encoding and integration of language material, and increase retrieval of information when needed for use” (P1)。 

Recently, Cohen (2000) displayed his recognition about learning strategies which are methods used to dispose of materials through identifying, discerning, and recombination。 It deepens the contact between materials and learners, triggering natural recalling of learning materials by enhancement of memory of learners about learning materials。 

2。2。2 Classifications of Learning Strategies

Many scholars have continually generated their theories about classifications in language learning strategies based on different criteria and approaches for many years。 Based on a summary of Chamot (2004), in earlier studies about learning strategies classifications, linguists tried to use their own observations to depict their ideas such as Rubin and Stern, depend on categories of research in first language contexts like O’Malley and Chamot, or make developments on a comprehensive series of language learning strategies through different origins like Oxford, whereas, more recently, the researchers such as Chamot and EI-Dinary tended to classify language learning strategies by think-aloud protocol analysis。文献综述

Therefore, in order to identify different classifications of language learning strategies systematically and clearly, there is a need to show some prominent classifications。

To begin with, Rubin (1981) separated language learning strategies into 2 major parts: direct learning and indirect learning。 As for direct learning strategies which also can be called cognitive strategies later, it includes six different types: classification/ verification, memorization, guessing/inductive inferencing, deductive reasoning, practice, while indirect learning strategies equals to social strategies which are taken by learners for totally benefiting from experience of learning, to organize their learning environment。 It consists of creating practice opportunities and using production tricks which include communication strategies。 

In terms of Bialystok (1978), there are four models of learning strategies: formal practice, functional practice, monitoring and inferencing used to address two kinds of linguistic knowledge: implicit linguistic knowledge—“the intuitive information upon which the language learner operates in order to produce responses in the target language”(P72) and explicit linguistic knowledge(containing whole language consciousness of learners and the standards used for admitting this category as an ability to demonstrate those facts, for example, grammar rules)。 In specific, formal practice concentrates more on a language form or systematic features, whereas functional practice centers in the usage of language in communicative situations, namely the meaning of the message。 Moreover, monitoring is a strategy of production like formal practice, while inferencing think highly of comprehension like functional practice。