What does "semantic shift" mean?

The term "semantic shift" refers to the phenomenon where a word changes its meaning over time, becoming something entirely different from its original definition. This process occurs due to various factors, including cultural changes, technological advancements, or shifts in societal values and norms. For instance, the word "nice" originally meant "foolish" or "ignorant," but over time, it has evolved to mean "pleasant" or "agreeable."

This concept emphasizes how language is dynamic and reflects the evolving nature of communication within a society. The other options do not accurately represent the definition of semantic shift; instead, they refer to different linguistic concepts, such as obsolescence, phonetic changes, and common usage, which do not encapsulate the essence of what a semantic shift entails.