ABSTRACT
A language may have different grammatical systems at different historical and field hierarchies; the grammatical functions of its words may also be different, and the criteria for classifying their parts of speech should be different too. To divide parts of speech, the first thing to do is distinguish whether a constituent is a word or not. But sometimes it is hard to tell whether a constituent is a word or not. Some dictionaries only recognize the universal hierarchies of the words that form words in different hierarchies and have different parts of speech. The classification of modern Chinese parts of speech should consider these different historical hierarchies and treat the constituents in different hierarchies differently. This chapter explains in some detail several cases of word identity determination with regard to the classification of parts of speech.
