Ask students for examples of pairs of words that are synonyms. Write them on the board. Go through the same process for antonyms. Then have students define synonyms and antonyms. Write definition on the board (Synonyms-words that have the same meaning as another word Antonym-words that have the opposite meaning.)
For example:
Target Word: Exhausted/Related Words: sweaty, exercise, strenuous, tiresome.
Target Word: dazzling/Synonyms: bright, sparkling, shiny, light reflecting.
After that discuss why learning synonyms and antonyms is useful in reading and writing (helps with reading comprehension and enables students to use more variety in their writing).