This paper studies the two English synonymous words "little" and "small," and their Thai equivalents n??j4 and lek4. In addition to monolingual and bilingual dictionaries, British National Corpus, Thai National Corpus and an English-Thai parallel corpus were used in this study. It is found that "little" and "small" and their Thai equivalents are not precisely identical in meaning. In addition, there are some meanings that can apply to all these four English-Thai synonymous words. Therefore, a Thai learner of English may not be able to simply equate the use of "little" and "small" with n??j4 and lek4, and vice versa. Moreover, it is also found that "little" and "small" can be translated into Thai with some other words rather than n??j4 and lek4. This indicates the complexity of meaning in which "little" and "small" can connect to other related meanings and be translated into Thai with other words. This study suggests that information provided in dictionaries alone is not sufficient. Learners should learn how to use corpora as a resource to enhance their lexical knowledge in both languages.