Language changes over time. Words, phrases, and expressions drop out of the modern vocabulary or are added to the modern vocabulary depending upon the social, cultural, technological, and political advances made in the world. The use of expressions like clichés, idioms, slang, euphemisms, and jargon can make a character appear more realistic and the story more interesting, but it can also create a stumbling block for readers of later generations if these expressions fall out of use.