How many words?

Exercise

Find the mistakes in the following text. Click on an incorrect word and type the correct word in the box. If you click a correct word, you will lose points.
The most goal is to know all of the language. However, even native speakers do not know all the vocabulary of the language. There are numerous vocabularies, such as those of nuclear physics or linguistics, which are known only by the small groups who in those areas. Still, it is to have some idea of how many words there are in the language. This is not an easy question to because there are numerous other questions which affect the way we answer it.