The average persons' vocabulary consists of 10,000 words, regardless of native tongue. Usually, this represents a mere fraction of the lexis of that language. English, for example, contains approximately 600,000 words, established by the Oxford University Press. This discrepancy, however, is partly due to relative simplicity of spoken language to written language. Additionally, one may understand more words than one uses, meaning that one's working vocabulary may not be representative of one's total knowledge of a language.
Vocabulary can be improved by exposure to new language information. Exposure through writing is especially effective, for it offers a greater context by which new words may become understood.
Dictionaries and other reference works may provide additional information.