A large vocabulary is important to be able to really enjoy a language. But how many words do you have to know?

'Crawl' level: 400-500 words, about 150
phrases. You can make yourself somewhat understood and understand slow speech.

Mini level: 800-1000 words and 300 phrases. Now you can speak relatively well and unstrained, and can read newspapers and books with the aid of a dictionary.

Midi level: 1500-2000 words and more than 300 phrases. What you need for day to day conversations. During the course of one day you need approximately this amount of vocabulary, and you can take part in serious discussions and understand what is being said at normal speed.

3000-4000 words: Sufficient for reading newspapers and magazines fluently.

8000 words: All you ever need. More words are not necessary in order to communicate freely and read all types of literature.

10.000-20.000: Active vocabulary in the mother tongue for cultivated Europeans.

50.000-100.000: Passive vocabulary (words you understand but don't use yourself) in the mother tongue for cultivated Europeans.

Source: A. Gethin og Ev Gunnemark,
"The art and science of learning languages", 1996.