Nation (2001) declares that knowing a word means knowing the member of the family of the word and by developing proficiency, the number of the members of this word family will increase.
In addition, research has shown that using associations in learning vocabulary is more effective than rote learning.
He also mentions that most researchers distinguish three main ways in which a learner’s vocabulary increase: through deliberately learning or being taught, through
learning by meeting in context, and through learning new words by gaining control of prefixes,
suffixes and other word building devices.