In linguistics, an interjection is a word or expression that occurs as an utterance on its own and expresses a spontaneous feeling or reaction.[1][2] The category is quite heterogeneous, and includes such things as exclamations (ouch!, wow!), curses (damn!), greetings (hey, bye), response particles (okay, oh!, m-hm, huh?), and hesitation markers (uh, er, um). Due to its heterogeneous nature, the category of interjections partly overlaps with categories like profanities, discourse markers and fillers. The use and linguistic discussion of interjections can be traced historically through the Greek and Latin Modistae over many centuries.