What is etymological fallacy? I coined this word to mean the tendency of English students and teachers to infer the meaning of an English word from its etymology. For example, I have heard several times an explanation about the difference between the two words: ambiguous and vague. According to it, if something is ambiguous it can be interpreted in two ways, whereas if something is vague, it is not clear and hard to understand. This explanation, so I should imagine, comes from an etymological understanding of the former adjective. The part "ambi-" means "on both sides." But this explanation is based on a questionable assumption: that the etymological meaning of a word is recognized and understood by the modern people who use it. I contend this assumption is totally false, for how many of us Japanese people today know that the Japanese word unagi, which means "eels" in English, is etymologically akin to another Japanese word anago (notice the similar pronunciation)? I can cite as evidence the explanation of the adjective provided by Oxford Advanced Learner's Dictionary. It says when something is ambiguous, it "can be understood in more than one way." So something ambiguous can be interpreted in three ways or four ways. So I propose that this assumption be dismissed and that all the explanations based upon it be reexamined.