All things you have to do to look up a definition of a word is just moving the mouse cursor over the word whose definition you want to know. You can see the definition as soon as you move the mouse cursor. It's real-time operation!

Would you like to learn the words you've found after you finish to read or finish your work? This history function is useful for this case. When you click some words, the definitions of them are registered to the history pane in the side bar. Because the definitinos remain in your sight, you don't have to search the same word again.

Click a menu 'View History', and you can get a list of words and definitions which is shown with excerpts from original documents and hyperlinks to it. It's your extremely personalized word book.

FireDictionary also accepts offline documents. You can generate a html format document from the clip board, so you can apply FireDictionary for Word, PDF or other offline documents.