Working to expand your vocabulary is a fundamental language learning task and one that is easily measured. You may need to learn more than 10,000 words and phrases to reach a university or professional level of fluency.
Following a system of better and more successful language learners you are supposed to measure your own steady progress towards your vocabulary goal, which is an important motivator.
Learning new words and phrases can be frustrating. New words are easy to forget and complex words and phrases can have subtle shades of meaning which vary depending on context.
Vocabulary learning is often handled in an inefficient manner by learners. They look words up in a dictionary and then forget them. They write lists which they never refer to. They have no record of what they have learned, and what they still need to learn.
Often learners study isolated lists of words and phrases in the hope that they will remember them for tests. There is an absence of method, measurement and planning.
You need to develop your own approach to the learning of words and phrases to dramatically speed up language learning.
A better system does not provide vocabulary lists with each lesson. You must take the initiative. Just as you choose what to listen to and read, you also decide which words and phrases from your listening and reading will be most useful to you.
By choosing your own vocabulary items rather than being spoon-fed, you will remember them better.