A major part of the Cambridge C1 exam is the , which tests your ability to change a word’s form. You should study how to transform base words into advanced forms: Vocabulary List | Cambridge English
If you have searched for the you are likely looking for a magic bullet: a single document that contains every word you need to know. The truth is more nuanced. While Cambridge does not publish a single, exhaustive "dictionary" PDF for students, they do publish essential official documents that serve this exact purpose. --- C1 Vocabulary List Cambridge Pdf
The Oxford 5000 includes the most important words for advanced learners. It is available as a free, downloadable PDF. A major part of the Cambridge C1 exam
Use their online search tool to filter by "C1" and export your own list. Oxford 3000 & 5000: While Cambridge does not publish a single, exhaustive