One very important dimension of vocabulary knowledge is receptive vs. productive vocabulary knowledge.
Receptive vocabulary knowledge refers to the ability to understand a word when it is heard or seen while
productive knowledge is the knowledge to produce a word when one writes or speaks. It is generally believed
that words are known receptively first and only after intentional or incidental learning become available for
productive use. Therefore, vocabulary knowledge should be regarded as a continuum on which a word grows
from receptive to productive status. Although little is know till now about the transfer from receptive to
productive mastery, it is generally believed that learners’ receptive vocabulary size is much larger than their
productive vocabulary size.