Free Online Dictionary Merriam-Webster

Merriam-Webster (http://www.merriam-webster.com) is a dictionary that supposes as Thesaurus, Spanish-English, Medical Dictionary.  When you search a word, you will see not only the meaning of the words but also Examples of INVOKE, Origin of INVOKE, Related to INVOKE(Synonyms), Rhymes with INVOKE.  If your English skill is beginner, you can also learn from the link "See invoke defined for English-language learners » "  This link will also allow you to listen the pronunciation of your searched word.