1. You can learn faster
A person with a good vocabulary does not have to look up in the dictionary for the meaning of words every other sentence and the flow of reading is not disrupted. When you read at a steady pace with minimal distractions, you enjoy reading with better comprehension too. Means, you can read more books in shorter time and learn faster than your competitors.
2. A Vocabulary Master is often a good writer and speaker
When you have appropriate words for everything you have got to say, you can speak with better articulation and write well. Words come facilely without having to think much for a simple phenomenon. You can paraphrase any piece of information in a way a five year old can understand and can even translate better.
3. You can become a great teacher
Whatever field you are in, there is always a need of a great teacher. In the military world as well as the peaceful monastaries, from super industrialized nations to under civilized nations, teachers are always scarce. A great teacher or master is always looked at with respect and gratitude. You can simplify things if you are comfortable with all the enigmatic words and make it easier for other people to understand.
4. You can sell anything you want
A great salesman is always in demand. I have heard somewhere, every person in this world is a seller, some sell their skills, some sell their time, some sell commodities, some simply sell their bodies and some even souls. But a vocabulary master can sell anything he wishes to sell as there comes a great power to persuade people along with a great vocabulary. And is is said that, a great salesman is one that can sell comb to a bald person.
5. You'll have better memory
When you have an extensive vocabulary, you can imagine every stuff you read immediately. You can engage your senses and make it realistic in your head. You can add colors and flavors to any lackluster story and make it interesting and memorable. And when you understand things and know the mechanism underlying, you'll no longer have to remember anything by rote memory.
So, the first thing you need to learn as a student or make your children learn while they are still young is to build a good vocabulary, extensive and large enough that you no longer need any dictionary. Once you are into it, the snowball effect continues and your pool of words accrue and become larger.
