The effects of vocabulary size on language comprehension
The knowledge of the words deriving from the 3000 most frequent English word families and the 5000 most frequent words provides a comprehension of 95% of word use, and knowledge of 5000 word families is necessary for 99.9% word coverage.
Second language vocabulary acquisition
Learning vocabulary is one of the first steps in learning a second language, but a learner never finishes vocabulary acquisition. Whether in one's native language or a second language, the acquisition of new vocabulary is an ongoing process. There are many techniques which help one acquire new vocabulary.