There are different ways of acquiring an extensive vocabulary, and one of them is working with corpora and word lists to either discover words in their possible syntactical contexts or see what other words belong to the same word family. Here are some of the online resources we consider helpful that you might use for this purpose.
The Academic Word List – The Academic Word List is a corpus that provides the most relevant 570 word families for academic purposes, excluding the most frequent 2000 words of English that you most probably already know and use. If you are aiming for a more sophisticated writing style in your term paper, this page is exactly right for you.
The Academic Collocation List – In a way, this is the advanced version of the Academic Word List, as it contains not only single words but also collocations consisting of verbs and nouns, adjectives and nouns, adverbs and adjectives, and many more. If you tend to combine the same words all the time, check out this 42-page PDF-document.
Corpus of Contemporary American English (COCA) and British National Corpus – These corpora allow users to find word usage patterns in authentic texts such as spoken texts, fiction, popular magazines, newspapers and academic journals, and make detailed comparisons between genres, varieties and word combinations. They are a bit complex in their usage rules, but practical in both linguistic analysis and understanding real-life usage.
Academic Phrasebank University of Manchester – This is a database of useful chunks for written work or oral presentations in the academic context. The database is divided into several categories that each come with subcategories, such as “being critical”, “giving examples” or “compare and contrast”.