C1 is advanced. Follow fast native speech, read academic texts, express yourself with real nuance.
Roughly 3–5 years of serious study.
C1 is advanced. Vocabulary doubles again to around 8,000 words, and the gains shift from quantity to quality: nuance, register, collocation. You learn that strong tea isn't powerful tea, that "I beg to differ" means something different from "I disagree", and that dilapidated, run-down, and decrepit are not interchangeable. Idiomatic expressions and phrasal verb networks become a major focus.
If you can read literature, follow fast native speech in any accent, and write a coherent argumentative essay, you're around C1. Most learners reach C1 after 3–5 years of serious study, usually combined with immersion. C1 is the level competitive university programs and white-collar employers ask for, and it's where IELTS Band 7 sits.
At C1 vocabulary acquisition becomes incidental: you pick up words from extensive reading, conversation, and noticing collocations. Use the list to spot blind spots and feed them to spaced repetition with full example sentences (not single-word cards). Focus on collocations rather than isolated words: heavy rain, make a decision, take responsibility. The shape of the language matters more than its individual pieces.