The understanding of inner speech nature formed in psychology is contradictory. This conclusion is due to the observations on comprehension and speech processes as well as to some studies' results. In order to overcome these contradictions the most widely spread views on the problem are analysed. It is hypothesized that the term "inner speech" is to be understood as sign component of consciousness resulting from interiorization of outer speech. It represents central speech core forming inseparable unity with image-bearing and emotional components.