Vocabulary

I think that the vocabulary is two sides; one is actual number of words in the memory, and the other is the link of the words with the meaning, situation and the relation with other relevant words.

We Japanese have studied English so long, so they have large number of words in their memory. But they are only linked with the meaning, not with the using situation.

This is one of the reason why we cannot speak English.

The situation is linked with words by explaining something with the words. And the link is strengthened by using it repeatedly.

This may be called "practice".
Practicing is the base of everything.

Animals forget every things, because the cells in the brain dies every second. And practicing is memorizing, saving some information to another new cell.

Practicing is the only way you can keep and develop everything.