You wouldn't want to "learn" a language from a dictionary - a dictionary is a "reference" book, not a teaching text. A dictionary could be used along with a good language book or course.

I wouldn't use any dictionary to learn a language, since its primary function is reference to a language that the reader already understands.

it's impossible to learn a language through a dictionary. for example i speak spanish and english perfectly but they never translate into each other perfectly. All languages build sentences differently. i could give you an example if you want.

1) A dictionary will certainly help you to learn a language. But it won't replace a course, normally. Also, the best dictionary to use will depend on the language. I personally preferred to use single language dictionaries than two-language dictionaries. Now, I rather use the internet as a reference. 2) You can check your spelling on Google, for instance your question: "Did you mean: the best dictionary to learn languages?" Source: http://www.google.com/search?hl=en&q=+the+best+dictionary+to+learn+langueges%3F&btnG=Search Alternatively, there are some (free) spell checkers and grammar checkers online, or with text processing software. 2) "The best online dictionary for learning any language: Google Image!" "There is a huge problem with almost every single dictionary you will come across. The translation is always wrong! Yep. Demand your money back! When you look up a word such as “voiture” from French, your dictionary may suggest “car”. But “voiture” doesn’t mean “car”. A “voiture” is “a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor…” which in English we happen to call a car. But it isn’t a “car”! That’s just a word, a set of letters. That voiture/car/coche/auto etc. thing is a concept. This is an important idea for learning languages. When you see a new word, which is spelt entirely differently from how it is in English, you may be tempted to just think yourself “Why do they make it so hard?? Why can’t they just use the English word?” Well, there is no universal relationship between an object and any particular word, even (gasp!) English words!" "Google Image to the rescue! Most of you may be familiar with http://images.google.com as just a quick way to get an image from the Internet to use in some document (like I just did with the computer image above). But it has much greater potential than this. As suggested a while back, over at Lifehacker, you can use Google’s Image search as a dictionary. Try it for my examples above (voiture, ordenador). Or try it with any word you are learning! Obviously it gets trickier when looking up verbs that are hard to represent as images or emotional concepts etc., but on the other hand it does much better at representing harder specific words that your cheap pocket dictionary or even the best online dictionaries can’t find. When using this, note that you should set Google image’s URL to the domain of the country that speaks the language you are learning whenever possible (this ensures Google doesn’t think you misspelt the word, or if there is a false friend or brand name etc. in English with that word)." Source and further information: http://www.fluentin3months.com/the-best-online-dictionary-for-learning-any-language-google-image/

Today I found the newest dictionary site on the web and I just felt I need to share it. KirzeN can be find at http://kirzen.com/. However it is still under development, I reckon the idea behind is just brilliant. You can find translations in more than 100 languages, and here comes the unique stuff; you can also watch videos and images related to that word you were looking for. It is the most useful thing that can help you learning a language and understand the meaning of a word, if you don't have a clue about it. Besides these, KirzeN has a Workshop where you have the possibility to upload pictures and videos, if you want it can show you or anything that is related to you. Later on, the etymological background of each words and phrases are going to be listed, chat rooms are going to help you to get connected with other users, and forums for discuss your thoughts. Now there are several hundreds of users registered already who you can browse by where they located or what language they speak. Try it; I hope you will find someone interesting. Check out KirzeN, you might be surprised! ;)

Search for translations in our free English dictionary or choose from the other, more than 40 foreign languages. Besides searching for translations in the dictionaries, you can browse pictures, videos and pronunciations uploaded by the users of KirzeN. Sign up and share your knowledge! In the KirzeN Workshop you can edit the online dictionaries and review that other members uploaded. http://www.kirzen.com