There are many reasons why vocabulary is important.
First, people judge you by the words you use. Like it or not, every time you speak to someone they are trying to figure out how competent, successful, and smart you are.
Research has shown that people are more likely to be judged as competent and smart when they speak with a good vocabulary.

Second, language and thought are inseparable. You need words to think and to think you need words. If you don't believe me, try to come up with a solution to a problem without thinking in words. You can't - it's just plain impossible. Language is the tool our minds use to think, plan, solve problems, and succeed.

Therefore, it follows that knowing more words gives your mind more ways to think about things and more tools to plan and solve problems. Having a better vocabulary literally improves your ability to think.

What tools do we have to improve our vocabulary?

There are many vocabulary building tools available that are effective in improving your vocabulary, but my purpose here is to turn to traditional and inexpensive ways that work better than most vocabulary programs. Reading is one of the most effective ways of improving vocabulary. If you are doubtful, then talk to a person who is well-read and another who doesn’t read much. You will see a marked difference. The well-read person might be shy or he might stammer, but he will seldom stop due to lack of a word. He won’t sprinkle ‘you know’ or ‘like’ in every sentence. When somebody uses too many ‘likes’, ‘ums’, ‘you knows’  or too spends too much time fumbling over a description in search of a word, it means that he or she doesn’t have an adequate vocabulary. An improved vocabulary makes you precise and articulate.

When you read, read everything. Don’t restrict yourself to the books you like to read. Read more diverse material to improve your vocabulary. This will not only make you smarter, but you will also have 90% greater chance of enriching your vocabulary. Trying something new becomes annoying and difficult as we grow up. Sometimes, we don’t feel like picking up a newspaper or a business magazine because we are not really interested in it, but if you want to improve your vocabulary, you will have to overcome this mental laziness and read more widely. You might be a little bored the first time, but with increased knowledge and understanding you may even start to enjoy these new areas of learning.

Another important thing that, we have to do is to know and teach students the differences between (BICS) Basic Interpersonal Communication Skills or conversational English and (CALPS) Cognitive Academic Language Proficiency or Academic English. By the same token, we should also teach students the differences among tier-one, tier-two and tier-three words. My plan here is to build a collection of practical resources, activities and handouts that help students expand their vocabulary.