“Among the factors that make new vocabulary more easily learnable by second language learners is the frequency with which the word is seen, heard, and understood. Paul Nation (2001) reviews a number of studies suggesting that a learner needs to have many meaningful encounters with a new word before it becomes firmly established in memory. The estimates range as high as 16 times in some studies. Even more encounters may be needed before a learner can retrieve the word in fluent speech or automatically understand the meaning of the word when it occurs in a new context. The ability to understand the meaning of most words without focused attention is essential for fluent reading as well as for fluent speaking.”