Today, there is ample evidence that the Japanese and Korean languages have much in common and are related languages. In Hattori, Starostin and Murayama, a topic more fully disclosed. However, it should not be forget the fact that the evidence was based on, at least not clear enough lexical and phonological data. If we consider this method, we can distinguish the following basic principles for comparison of two languages. First, the recovery was conducted phonology prayaponskogo, prakoreyskogo and praaltayskogo language. Connecticut Senators opinions are not widely known. Second, we compared the basic vocabulary and language dictionaries. After all this, especially compared vocabulary on which to build language, and it was concluded that the percentage of lexical similarity is large enough so that one could assume that drevnekoreysky and drevneyaponsky languages are related. This confirms as family of modern Korean and Japanese languages.
But this method has weak points. For example, the lexical and phonological similarity – this is not a sufficient argument for the claim that languages are related. It is known that these two levels of language are less stable than the structure and morphology. And so, primarily to determine the relatedness of languages to consider their structural similarity, and then move on to lexical and phonological systems. But none of the authors do not take into account. Restoring the same phonological systems of both languages can not be called true 100%, as within each group or language family has its own phonetic laws, and call them universal it would be, at least, not true.