Euphemism is a generally innocuous word or expression used in place of one that may be found offensive or suggest something unpleasant. Euphemisms are used to soften or hide unpleasant topics like disability, sex, excretion, and death. They evolve over time through processes like circumlocution, taboo deformation, and semantic change. There are several types of euphemisms including abstraction, indirection, litotes, mispronunciation, modification, personification, and slang. Euphemisms differ from idioms in that euphemisms substitute agreeable expressions to avoid offense, while idioms have figurative meanings separate from their literal definitions.