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