All of the foreign language dictionaries that I have seen, such as Japanese/English and English/Japanese dictionaries, are just translations from one language to the other. Anyone who has studied a language which is not related to their native language will know that these dictionaries are often not helpful because they will give you several different words and you have no idea which is the right meaning for the sentence you are studying.
There are 2 kinds of uselessness.
1. Several words/translations which have relatively the same meaning.
2. Several words which some (or all) have different meanings in your native language.
The first one is a problem because if you want to remember (study) the meaning of the foreign word, you might try to remember more than one word. Really, in that situation, you would only need one word. But which one should you choose?
The second one is a problem because you will need to remember the different possible meanings for the word, instead of just associating it to one word. If you only choose one meaning, you won't be able to understand the sentence when the word is used closer to one of the other possible meanings.
Of course, I have heard many people recommend that you should start using a monolingual dictionary as soon as possible. This would mean, for me, looking up a Japanese word in a Japanese dictionary and reading the entry entirely in Japanese as any Japanese would do.
But my idea is for those who are not ready to do that. After all, you need to be at intermediate or higher in your studies.
My idea would apply to the Japanese/English type of dictionary and not the English/Japanese type. When looking up a foreign word in the dictionary, instead of being given several translations, it should have an actual definition. With a definition, you could get a feel for what the word means in the foreign language, but you would read it in your own language so you can completely understand it. I think this would be more effective than just a translation because your brain would process the information more and then you would think about what words that this meaning could apply to in your own language.
Now, to illustrate my point.
Looking up the word 全部 in the goo online dictionary, you find this for the entry:
all; the whole [entire]; total; every; 〔副〕all; wholly; entirely; altogether
This is an example of uselessness number 1. Do I really need four translations to understand the meaning of this one Japanese word? (Actually, this dictionary is solely intended for Japanese speakers.)
So, if I look up this same word in a dictionary intended for English speakers what will I find?
Here's what I find in the Random House dictionary (Seigo Nakao).
zenbu 全部 1. pron. all; everything.
2. adj. all
OK, so this dictionary has used only two words to define the meaning. But which does it really mean? Does it mean all or everything?
Now, looking at the definition in the Japanese only dictionary entry on goo, we get this kind of meaning:
(translated by me)
All of a matter or things. All. The whole body.Now I get the feeling that this word has to do with parts. Something which is made up of parts and refers to all the parts. So, if I am correct, would you want to use this word to refer to water? If there was a gallon of water and the question was asked, "How much of it should I drink?", I know I wouldn't say in English, "Drink all the parts of it!" Likewise, I think I should avoid using this Japanese word in the same situation. I should use a more appropriate word.
The opposite of one part.