Fast mapping is defined as a process of quickly determining a word's meaning, which facilitates children's vocabulary development ; process of acquiring new words rapidly; ability to learn new words based on very little input. Moreover, Fast mapping, refers to the process children engage in when they hypothesize a meaning for a newly heard word on the basis of hearing the word once or at most a few times. It is teh formation of a rapid, initial, partial understanding of the meaning of a word by relating it to the known vocabulary and restructuring the known-word storage space and its related conceptual categories.