This study focuses on the usages of YORU (因・依・仍・由・縁) found in Fudŏki.As a result, the ideographical usages can be distinguished by prepositions 因, 依, 由, and 縁 that all come in front of the words that explain basis, cause, and reason in the form of “…yorite,” and conjunctions 因 and 仍 that deal with how the behavioral and conditional cause and reason of the first part of the sentence results into the second half of the sentence in the form of “yorite.” Also, 由 is ideographically expressed as ゆゑ and holds the usage of a noun to explain the cause and reason itself. In conclusion, it is clear that 因, 依, 仍, 由, and 縁 in Fudŏki are Chinese characters chosen to be used in variously to define and explain the cause and the reason of the origin of mountain names, river names, plain names, and farm field names, and record passed down by elders.Moreover, along with the usages listed above, 依 holds verb meanings “to come closer” and “to entrust somebody,” 縁 holds noun meanings “around” and “vicinity” and a verb meaning to express that something is around, and 仍 plays a role as a conjunction to combine sentences by using “yorite” in the first part of the sentence to emphasize the second half in terms of rephrasing a sentence.As a result, it is necessary to know that the editors of Fudŏki had a common awareness of the meaning of words and can be seen that words were chosen carefully and appropriately according to the subject and the context.