Currently, there are a variety of researches on corrective feedback, especially on recasts. Most of researches are experiment-based and depend on the certain context. This paper addresses the question of "Is recast the most effective form of corrective feedback?" by two of Second Language Acquisition (SLA) approaches: cognitive approach and sociolinguistic approach. Empirical research will be used as complement. Theoretically speaking, SLA hypotheses in cognitive approach exist disagreements. Interaction hypothesis favors recast while both input hypothesis and output hypothesis doubt the effectiveness of it. Sociolinguistic approach underscores the significance of appropriate and timely corrective feedback and does not give more credit to certain strategy. Both approaches provide the pedagogical implications and elements to take into account for adopting recasts.

With the advancement and prevalence of computer engineering, corpus-based approach of language analysis is on the rise. In this study, corpus-based approach is being adopted to compare two verbal synonyms-obtain and gain in terms of genre, colligation, collocation, and semantic prosody. The online tools, such as Sketch Engine, BNC Web, and Just the Word, are been adopted. The differences of two synonyms are as following: Noun is more collocated with obtain and passive voice pattern with preposition is more widely used. The verb form gain is collocated with abstract noun and most of them are endowed with the positive semantic prosody. It is also found that Oxford Dictionary failed to add the semantic prosody and dropped the frequently used collocation such as "obtained by pretence". For ESL (English as Second Language) teachers, they should be cautious in the traditional practice of explaining meaning to leaners by offering synonyms. Moreover, semantic prosody should be taken into account in translating English into Chinese.