Antonyms are words that have opposite meanings, such as courage and cowardice. When you go beyond your dictionary to consult a thesaurus, a book or computer program that lists synonyms, remember that no two words have exactly the same meanings. Therefore, you should use synonyms carefully, making certain that the connotations of the synonym are as close as possible to those of the original word. Idioms Dictionary entries often show how certain words are used in set expressions called idioms. This information is necessary because the meaning of such expressions cannot always be determined from the words alone.
Dictionaries also indicate the idiomatic use of prepositions.
Where such labels involve value judgments, dictionaries differ. When no other reference works are handy, dictionaries can be excellent sources of general information. If you want to find out the year in which John Glenn orbited the earth, you can look up the entry Glenn, John. If you need to find out for whom the Davis Cup is named, you can look up Davis Cup. To test the research capability of your dictionary, use it to answer the following questions.