What does "not black and white" mean in the answer? the existence of frontier words greatly affects estimates of the size of one’s vocabulary. If someone has a dim sense of the meaning of a word, does he know it or doesn’t he? Clearly, the answer is not black and white. if I want to know how much vocab i need to know, and what criterion judges I know the word, and if i have a dim sense of meaning of a word, doesn't he know the word or not, the answer is not black and white. it says that he doesn't know the word for example ,like truculent and supercilious i know the generous meaning but i don't know what situation to use and allocation etc. that means i don't know the word or counting I know the word. thank you very much....