Macmillan Dictionary

Macmillan Dictionary is free and it doesn't require any subscripition in order to be fully used. In terms of resources available, we can access "Language Resources", "Pronunciation" (through listening and phonetic transcription), "Clear Definitions", "Red Words and Stars", "Thesaurus", "New Words", "Real Examples" among others. It should be highlighed the fact that it in "Real Examples" section, it provides rather clear explanations on how to use a word in a very specific context of grammar structure, eg the collocation of an adverb in a sentence.