The purpose of research described in the current study to investigate the impact of structure knowing on two types of test, i.e. word-meaning test and fill-in-the-blank test, their correlation and procedures on both short-term and long-term retention of vocabulary items. The importance of the present study, to test the condition that learners are not allowed to use guess strategy or randomly answer the tests and they should give reason semantically for their answer, otherwise their answer, even is correct, is not scored. The population for subject recruitment was all undergraduate students from second semester at large university in Iran (both male and female) that study English as a compulsory paper. In Iran, English is taught as a foreign language.