Macmillan English Dictionary. A very good free option for advanced learners, with featured words and clickable pronunciation guides. You can set the default option for British or American English here.

• There is now a thesaurus function integrated into the Macmillan dictionary as well.

Longman Dictionary of Contemporary English Online. Contains useful corpus examples for each word.

The Cambridge Dictionary website links to a number of useful dictionaries and reference guides. You can also set English-German and German-English options.

• Cambridge Advanced Learner's dictionary. This is the default resource. It has a handy browsing function and each entry offers both British and American pronunciation.
• Cambridge Learner's Dictionary (A2-B2 resource)

Oxford Advanced Learner's Dictionary. You can toggle between English and American English on the main search bar. The  [paid] Oxford Learner’s Dictionary of Academic English (OLDAE) is also highly recommended.

• The Oxford Lexico dictionary is a collaboration between Oxford University Press and Dictionary.com, aimed at first-language English speakers but with useful content for advanced learners as well.
• This dictionary is also the source of many of the definitions you will find by simply entering a word into Google.

Collins Cobild English Dictionary. A good all-rounder, pitched somewhere between first language and monolingual learners. There is also a thesaurus function and an English-German option. And a Scrabble list!

Merriam-Webster. The standard American English work. It also has a thesaurus function.

• Merriam-Webster offers a simpler learner dictionary as well.

Oxford English Dictionary. Known as "the definitive record of the English language". It contains etymology and history as well as definitions. The university has a subscription which you can access while logged into the campus network.

Vocabulary.com. Definitions with up-to-date real world examples from sources such as the New York Times.

Ozdic.com. A useful collocations dictionary and reference work, with a straightforward interface.

Urban Dictionary. A crowd-sourced reference for slang, colloquial expressions and very modern English.

Grammar

English Grammar Today is another option on the extensive Cambridge Dictionary website. It functions via a search box as well as an A-Z browsing function - useful if you don't know the exact term for what you want! British English only.

There is also a useful Grammar Guide from Oxford Dictionaries - the interface is slightly less crowded than the Cambridge version. British English only. (Note that the explanations are less detailed than in English Grammar Today.)

Collins Easy Learning English Grammar is a print resource that is also freely accessible online. (Just look for the table of contents on the left. It begins with parts of speech.) The resources are available as (paid) e-books as well.

Grammaring.com* - start with the list of topics.

*What sort of site is this? To quote: "Grammaring.com is a shortened version of the e-book The Grammaring Guide to English Grammar. While it does not contain timeline diagrams, quotes, and exercises, which come with the e-book version, it has some extra features that make it a practical resource for intermediate to advanced students of English as a second or foreign language."

The Internet Grammar of English  is an online course in English grammar written primarily for (British) university undergraduates - it is very helpful if you'd like more information from a linguistics perspective.

Vocabulary and Expression

Academic Phrasebank. This database, created by John Morley at the University of Manchester, has an extensive collection of useful phrases for academic speaking and writing. There is also a version that can be purchased and downloaded for off-line use.

The Academic Word List and the Oxford Phrasal Academic Lexicon are both useful word collections linked to dictionary entries.

SKELL - Sketch Engine (language corpora software) for language learning. The simplifed student interface has a lot of interesting options for exploring and describing authentic language use. (If you don't really know how to use a corpus, then this is a good place to start.)

Grammar Guides

* Academic English Online has an excellent selection of practice tasks.

* The resources at Global Pad (Warwick University) are also good for developing a range of academic skills, including writing.

* The resources from Using English for Academic Purposes for Students in Higher Education (Andy Gillett) provide a very helpful overview.

* The Academic Writing in English website put together by Lund University in Sweden also contains a lot of useful information about common writing issues.
 

Which words?

At university level there is no single list of vocabulary for students to learn, and you are expected to be working on your vocabulary range throughout your degree/s. ⇒ However, a good place to start is with the guidelines here. Further links can be found below.

• Building your academic vocabulary
  • with exercises
• General EAP vocabulary exercises (based on the Academic Word List [AWL])
• Techniques for learning vocabulary
  • with exercises