MORE DICTIONARIES TO USE ONLINE

Have you ever used a visual dictionary? Here is a link: visual dictionary

You don´t know the correct pronunciation of a word, here is a link to a free online  dictionary English pronunciation

Dictionaries: Thesaurus

What does Thesaurus mean? “It’s a book that lists words in groups od synonyms or related words” . You can use it to enrich your vocabulary.
 If you’re writing the same word again and again in your essay, you should look up  synonyms in a thesaurus.
Here are some links to Thesaurus:

https://www.collinsdictionary.com/dictionary/english-thesaurus

https://www.merriam-webster.com/thesaurus

https://en.oxforddictionaries.com/

-

COLLOCATIONS DICTIONARY ONLINE

A collocation is made up of two or more words for example: to make the bed , to save time, etc.
If you use collocations, your English will sound better and more natural. There are so many collocations that it's really so difficult to give you a list of them.

Here you have a link to an online collocation dictionary: http://www.ozdic.com/

ONLINE DICTIONARIES

Online dictionaries are very useful when studying English because they give you the meaning, synonyms, audio pronunciation, example sentences, etc. 
Here you have some links which can help you:

http://dictionary.cambridge.org/us/

http://www.dictionary.com/

https://www.collinsdictionary.com/

http://www.macmillandictionary.com/

https://en.oxforddictionaries.com/