ABSTRACT
One view holds that a part of speech is concerned with distribution, and that its essence is distribution. Scholars attempt to use the similarity theory to explain the distribution nature of a part of speech, thinking that it is collected according to the distribution similarity of words. The reason why words have identical or different grammatical distributions is that they have identical or different expressional functions and semantic types, which are the intrinsic nature of a part of speech. The view that distribution is the nature of a part of speech cannot explain why words distributing differently in different times and languages yet belong to the same part of speech. The view that the nature of a part of speech is the combination of its expressional function, semantic type and syntactic function can produce a reasonable explanation: because they have the same expressional functions and semantic types.
