According to Balkcom (Balkcom 56), cooperative learning is a successful teaching strategy in which small groups, each with students of different levels of ability, use a variety of learning activities to improve their understanding of the learned subject. Each member in a group is responsible not only for learning what is taught but also for helping group mates learn, thus creating an atmosphere of achievement.

G. M. Jacobs in his famous book The Teacher’s Sourcebook for Cooperative Learning regards cooperative learning as principals and techniques for helping students work together more effectively. (Jacobs, et al. 30).

According to Slavin (Slavin 1995, 23),cooperative learning is a variety of teaching methods, in which students work together in heterogenous groups to achieve a common goal. The idea shared all cooperative methods is that students work together to learn and are responsible for their teammates’ learning as well as their own. 

In his book, Cooperative learning-theories, Research and practice, Slavin (Slavin 1995, 45) reviewed several widely used cooperative learning methods and summarized characteristics of cooperative learning as “group goal”, “inpidual Accountability”, “equal opportunities for success”, “team competition”, “task Specialization” (though not all cooperative learning methods satisfy all the characteristics).

Coelho(Coelho 24) held a view that cooperative learning is an approach both to education and a repertoire of learning strategies. In the narrow sense, cooperative learning is an approach to organize small group work in classroom, which encourages students to take responsibility for their own and each other’s learning. In the broad sense, its implication extends well beyond the walls of the classroom or school, affecting the development of not only the whole child but also the whole society. In cooperative learning, social skills should be emphasized as well as learning academic content and skills. Four components are vital in successful classroom collaboration. They are group formation and management, task design, the social components and exploratory talk.

According to D. W. Johnson and R. T. Johnson(Johnson 1994,35), cooperative learning is the instructional use of small groups so that students work together to maximize their own and each other’s learning. Different from competitive learning and inpidual learning, in cooperative learning situations students are working together to accomplish shared goals. Among the goal attainments there is a positive interdependence: students perceive that they can reach their learning goals if and only if other students in the learning group also reach their goals.

Of all these definitions of cooperative learning from different researchers, common ideas can be generalized, though their focuses various on it. That’s to say, cooperative learning is a effective way to promote students’ learning ability and levels with small groups. Each member of a group is supposed to make contributions to his group and do a favor to other members, helping create a harmonious atmosphere. The standard to measure a completed task is to ensure that all group members have take in the knowledge of the lesson.