roar – v. to make the loud sound of a wild animal

decibel – n. a unit for measuring how loud a sound is

hypothetical – adj. involving or based on a suggested idea or theory

construction – n. the way words in a sentence or phrase are arranged

subordinate clause – n. A subordinate clause is a clause that cannot stand alone as a complete sentence

blog – n. a Web site on which someone writes about personal opinions, activities, and experiences

Europa – n. an icy moon of the planet Jupiter

tidal – adj. rising and falling at regular times