Semantic Change
Semantic change happens when the definition and usage of a word shifts over time. There are multiple types of semantic change, including broadening, narrowing, euphemism, and taboo.
Broadening
Broadening occurs when a word that used to mean something specific gains a more general meaning.
For example, the word “holiday” used to refer specifically holy days, i.e., religious days of significance. Now, it can mean any day of celebration. It can also be used to refer to a vacation (e.g., to go on holiday), depending on your dialect.
Narrowing
Narrowing is when a word that used to have a broad meaning becomes more specific over time.
One example of this is “meat,” which used to mean almost any kind of food. In medieval and early modern Europe, dairy products were often referred to as “white meats.” Over time, of course, the meaning of “meat” has narrowed to only refer to animal parts, namely muscle. In some contexts, it can also exclude fish and poultry and refer exclusively to the flesh of mammals.
Taboo
Sometimes, words can shift to becoming taboo, i.e., avoided due to offensiveness, impoliteness, or other social discomfort. This happens most notably with terms dealing with bodily functions, sex and anatomy, and death.
One example of a word shifting to become taboo is “retardation.” At one point, this was a neutral and medically accepted term for intellectual disabilities. Over time, however, it developed a derogatory connotation and is now considered offensive and unacceptable in any context.
Euphemism
Euphemism (from Greek “eu-“, good/well, + “pheme”, speech/utterance) is the replacement of taboo terms with more socially acceptable language. This occurs in all the same areas as taboo.
Instead of using the word “die,” we can say that someone is at rest or no longer with us, or has passed, departed, crossed over, etc.