Have you noticed how many terms there are for just one word? There could be anywhere from two to twenty terms or meanings for one word. It depends on if it is an expression or what the context is trying to convey. That’s why books now have to include a glossary of terms.
In any given language there are many terms for an individual word, and the way of determining the meaning of the term is to see how it is used in context. This is true as well when talking about technical terminology as well. That's why you will find dictionaries that are specialized like medical terminology, or engineering technology, or even at the oxford English dictionary. Today it's not only important that most dictionaries be up to date and that all specialized terminology be defined but, it is also important to make such terms more readily available to users. Hence the need for frees the free online dictionary or the online medical dictionary.
Another reason dictionaries have become indispensable is because the Internet has made the world market smaller. It is much easier to do business across nations, and if you have noticed the internet reflects that with its language dictionaries like the Spanish to English dictionary, the English to French dictionary, and even the Italian English dictionary. Even Webster’s online dictionary seems to be more complete than the hardback or paperback ones.