SUMMARY
The positive role of corrective feedback is always emphasized in the second/foreign language learning.The purposes of the present study are therefore to recognize learners' lexical errors (the use of inappropriate or incorrect words, phrases or compound words), identify lexical-structural errors (different forms of words (base, noun/verb, adjective/adverb), and word order in a sentence, study and compare the effect of teachers' immediate and oral corrective feedback towards learners' lexical errors on the basis of Lyster and Ranta's corrective discourse model (1997), determine more and less effective types of feedback on the base of learners' response to each type.For this purpose, some intermediate English learners were selected and then were randomly divided into seven groups.Then, all these learners participated in vocabulary pretest. Then, they received different types of corrective feedback provided on the basis of Lyster and Ranta's patterns.The first group was the control and did not receive any types of feedback; the second group received explicit correction, the third group recast, the forth group clarification request, the fifth one metalinguistic feedback, the six one elicitation and the last group received repetition feedback.At the end of the study, all groups were compared with each other by conducting a posttest.The results of variance analysis which has been done by using SPSS software, showed that there was a significant difference between the groups which received negotiationtechnique(clarification request, metalinguistic feedback, elicitation, and repetition) and the control.As far as the vocabulary proficiency of the learners was concerned, there was a significant difference (p=0.05) between the pre and post-tests of each groups that received negotiationtechnique.However, there was no significant difference between the group which received explicit correction and the one which received recast.Also, regarding the vocabulary proficiency, no significant difference was observed between the two groups which received corrective feedback and recast.Correcting the learners' lexical errors by negotiation, especially elicitation, is more easier than other types of feedback.