Abstract：Language is the basic element of the development of culture, and is also the basic component of the theoretical philosophy. The Greek word eimi is such a gene of Western philosophy. It attracted great attentions of the Chinese philosophical scholars in the long-lasting discussions about ''Being,'' because a serial of philosophical and metaphysical problems in the later Western history, and even some fundamental problems of modern Chinese philosophy, originated from this word. Greek language emerged before 13th century B.C.. In the 17th - late 18th centuries, linguists assumed that Indian and European languages originated from a common primitive language, the Proto-Indo-European language, and thus Greek could be traced back to this primitive language. Different from Chinese language or other non-Indo-European languages, Greek is an inflected language, whose grammar is a specific assembly of forms of thinking, structures, inflections and suffixes. In the earlier discussions of the academic circles, some scholars confused the root and the stem of eimi, and some even advocated -re-inventing Chinese translations for eimi according to its inflections as a copula. In fact, ''root'' is a concept of etymology but ''stem'' is that of morphology. Words belonging to Indo-European language are assumed to have common sources which are rooted in proto-Indo-European. If we can clarify the root of eimi, then we can also apprehend the primitive significance of eimi. It is generally recognized that eimi has two closely related roots, es- and bhu-, which are ancient and independent notional verbs, including the meaning of ''to exist in somewhere''. C. H. Kahn holds that only es- is the only root of eimi, while bhu- is the root of verbs of ''to become,'' or ''to grow''. Despite the arguments on how many roots are involved, it is clear that eimi has more than one significance of ''to be'' (as a copula). One of the oldest significances of the root es- is to signify location, meaning to occupy a position in some place, from which other general significances were derived. Many linguists believe that the independent and existential usage of es- is more primitive than its copula usage which is later and derivative. This dichotomy also influences the understanding of ''Being'' in the English-speaking world. It is doubtable of C. H. Khan's attempt to determine the primitiveness of eimi as a copula by the statistical frequency of it in Homer's works. To settle this problem, the genealogical method is more reliable. The emergence of copula is a later fact (than that of notional verb) in all sorts of national languages, and it is also a symbol of human's mind stepping into the logical stage from pre-logical stage.