challenge – v. to test; to compete against
grammar – n. the whole system and structure of a language
stress – n. the act of noting the importance of something
comedy – n. a play, movie, television program, or performance that is meant to make people laugh
journalist – n. a person who collects, writes, and edits news stories for newspapers, magazines, television, or radio
casual – adj. unofficial, informal or unceremonious
negation – n. grammar to make (a word or phrase) negative
certain - adj. fixed or established; known for sure