- Dictionaries: some of the dictionaries I tend to recommend at B2 level and upwards are the Cambridge Dictionary (https://dictionary.cambridge.org/) and the Oxford Thesaurus (https://en.oxforddictionaries.com/, choose ‘Thesaurus’ in the dropdown menu). Ideas on how to use a dictionary here to improve writing tasks here: https://natalialzam.wordpress.com/2016/12/06/how-to-improve-your-writing-tasks-b2-c1/
- Grammarly (https://www.grammarly.com): Add-on which checks for spelling mistakes, and suggests possible grammar mistakes through Artificial Intelligence. Its suggestions tend to be accurate/useful.
- Fraze.it (https://fraze.it): A database of online newspapers and magazines which may come in handy when trying to make sure that a given collocation sounds natural. Type your collocation into the search box, and if it can find those words, it will yield real examples where this expression appears. Once there, you can also click for more context. If your collocation exists, you will find a list of examples; if it does not, or is not very frequent, no or very few examples will appear.
- Flax (http://flax.nzdl.org/greenstone3/flax?a=fp&sa=collAbout&c=collocations): enter a word, and how words form into collocational patterns will be revealed by looking across different academic and social corpora.
The following links provide further ideas and resources on how to check whether the language produced sounds natural, or to widen the range of vocabulary used to meet the requirements of B2-C1-C2 levels: