We know the following fact that

I - words used in reading, 

II - words used in auding,

III - words used in speaking,

IV - words used in writing.

The main aim of teaching vocabulary is assimilation of the meaning, form of the words and its usage in oral and written speech – that is formation of lexical habits. People can have many aptitudes, but without a large and precise English vocabulary to express them, they cannot take full advantage of these abilities. Unlike aptitudes, vocabulary is not a natural ability; it can be improved if one is willing to make the effort to do so. [7,90]

Building vocabulary is a powerful way to enhance your life and career. Learning how to build a better vocabulary can be a pleasurable and profitable investment of both your time and effort. At least fifteen minutes a day of concentrated study on a regular basis can bring about a rapid improvement in your vocabulary skills, which in turn can increase your ability to communicate by writing, conversing, or making speeches. Acquiring a large vocabulary can benefit you in school, at work, and socially. It will enable you to understand others' ideas better and to have the satisfaction of getting your thoughts and ideas across more effectively. Of course, you already know thousands of words, and you will continue to learn more whether you work at it or not. The fact is that many of the words you know were probably learned simply by coming across them often enough in your reading, in conversation, and even while watching television. But increasing the pace of your learning requires a consistent, dedicated approach. If you learned only one new word a day for the next three years, you would have over a thousand new words in your vocabulary. However, if you decided right now to learn ten new words a day, in one year you would have added over three thousand to what you already know, and probably have established a lifetime habit of learning and self-improvement.