In this study, how knowledge is mentally processed in the course following perception by attention, which phases it goes through, where it is stored, for what reasons forgetting happens are mentioned, and some mnemonic devices providing coding words in a foreign language effectively and remembering them for long were explained by some example practices usable in classroom. The main problem experienced by a lot of students in learning a foreign language is that the words learned are forgotten, namely, the permanence of the relevant words are short. The permanence of the knowledge obtained through simple repetition is short. Some mnemonic devices are used for the resolution of this problem.Research shows that the fact that mnemonic devices establish a semantic relation with either vocal or visual symbols enhances the permanency of words.While coding is mostly carried out by visual symbols in the Chaining and Loci Methods, words are coded along with both visual and phonetic elements in the Pegword Method. The method used most in teaching new words is the keyword method, in which vocal similarities in both the native and target languages are made use of. In this method, visual symbols are used actively. It can be seen that, in general, these techniques have a more significant contribution to coding knowledge, recalling the knowledge required, and the rates of permanency in the brain of the knowledge learned compared to the methods of simple repetition. Interpreting new words in a foreign language by connecting them to a known word through these ways of learning and reconfiguring them by processing with visual and verbal symbols ensure remembering new words for a long time. That’s why it is thought that it will decrease the rate of forgetting words to support foreign language learning with mnemonic devices.