The more vocabulary you know, the more you will be able to improve all aspect of communication. We will be more able to express one's self. It may be through reading, writing, listening and speaking.
Vocabulary is important in writing. You should know that vocabulary has a great impact whether you are making some communications at work where everything should documented or making some reports for school.
You will not be able to understand the word without knowing its definition or meaning. Vocabulary is also vital in reading development as it contributes comprehension to the reader.
In speaking, it is important to use the right words to be able to make a clear communication. You will be able to convey what you mean when choosing the right words in order to avoid confusion. And a good listening skills makes a smooth communication.