Since strategy is a general way towards problems, learning strategy is more concrete。 Linguist Stern says from the perspective of approaches: “In our view language strategy is best reserved for general tendencies or overall characteristics of the approach employed by the language learner, leaving techniques as the term to refer to particular forms of observable learning behavior。” He pides a line of strategy and skill, and the former is the general tendency of language learner, while latter is specific behaviors in learning which can be observed (Stern 5)。 However, other researchers have used the definition opposite to Stern。 

As for whether learning strategy is thought as behavioral or as mental, cognitive Psychologists Weinstein and Mayer say from the angle of process that learning strategies are “the behaviors and thoughts that a learner engages in during learning that are intended to influence the learner’s encoding process” (Weinstein and Mayer 315)。 They thought learning strategy is to be perceived as both behavioral and mental。 But linguist Oxford indicates that learning strategies are “specific actions taken by the learner to make learning easier, faster, more enjoyable, more self-directed, more effective, and more transferable to new situations” (Oxford 8)。 He considers it as essentially behavioral。 Also, while others mainly think the study of Second language can motivate the use of learning strategy, Oxford suggests the usage had emotional effect。

Another perspective is whether learning strategy has direct or indirect influence on language learning。 Linguistics Wenden & Rubin define it from the perspective of usage and regard it as “any sets of operations, steps, plans, routines used by the learner to facilitate the obtaining, storage, retrieval, and use of information” (Wenden & Rubin 19)。 They thought it has direct influence on learner。

Also, researchers have different ideas on whether learning strategy is to be seen as conscious or subconscious。 Linguists O'Malley & Chamot think “Learning strategies are techniques, approaches or deliberate actions that students take in order to facilitate the learning and recall of both linguistic and content area information" (O'Malley & Chamot 71)。 They stress the intentional and conscious behavioral feature of language learning。 And in Cohen’s point of view, learning strategies are “learning processes which are consciously selected by the learners” (Cohen 5)。 So Cohen only regards conscious behavior as a strategy while habitual one is just referred as a process。 However, some researchers like linguist Rod Ellis (1994) considers learning strategy may start as conscious tactic and develop into subconscious strategy。

From above, it can be seen that researchers don’t reach an agreement on the definition of language learning strategy, and the main differences are as followed: whether learning strategies are regarded as behavioral or mental or as both; whether strategies are conscious or unconscious; whether strategies have direct or indirect effect on language learning。 Since it is difficult to give a comprehensive definition, American linguist Rod Ellis (1999) gives some characteristics of learning strategies:

(1) Strategies refer to both general approaches and specific actions or techniques that are used to learn second languages。

(2) Strategies are problem-oriented, which means the learner deploys a strategy to overcome particular learning problems。

(3) Learners are generally aware of the strategies they use and can identify them if they are asked to pay attention to what they are doing or thinking。 

(4) Strategies involve linguistic behaviors (such as requesting the name of an object) and non-linguistic ones (such as pointing at an object so as to be told its name)。 

(5) Linguistic strategies can be performed in both the L1 and the L2。  大学生英语学习策略研究(3):http://www.youerw.com/yingyu/lunwen_158175.html