DERIVATION: In a dictionary, the derivation is the section which shows the origin and historical development of a word. It is useful for gaining a full understanding of a word.

IDIOM: A way in which the words of a particular language are joined together to express a thought. Usually, the meaning of an idiom is not equivalent to the sum of the meanings of the individual words. For example, the idiom "every dog has his day" means "something good or lucky happens to everyone at one time or another". Being able to find these specialized meanings of a word is very important to fully understanding the English language.

TOEFL and TOEIC: The TOEFL (Test of English as a Foreign Language) and TOEIC (Test of English for International Communication) tests are widely used to evaluate the English proficiency of people whose native language is not English. TOEFL and TOEIC are registered trademarks of Educational Testing Service.