Semantics is the name for the scientific study of the meaning of words and sentences. Semantics is closely associated with the disciplines of linguistics, logic, and philosophy.
One aspect of word meaning involves the ways words can be semantically related to other words. Examples of semantic relations include synonymy, or sameness (big-large); antonymy, or opposites (big-little); hyponymy, or subclass (rose-flower); and part-whole (handle-cup). Another aspect of word meaning is polysemy, the property of having many meanings. Foot and head, for example, are words with multiple meanings. The meanings of words change over time. Historical semantics is the study of these changes. For example, deer once referred to animals in general, and starve once meant die. Etymology is the study of the origin and development of words.
The meanings of sentences result from word meaning and syntax—the way words are put together. In Cats chase dogs and Dogs chase cats, both sentences have the same words and the same structure. But in the first example, we understand that cats are chasing dogs, while in the second we understand that dogs are chasing cats.
Formal semantics, which comes from philosophy, is concerned with truth conditions—the view that to know the meaning of a sentence is to know all situations and conditions under which it is true.
Entailments and presuppositions are another part of sentence meaning. Entailments are relations that connect statements. Whenever statement A is true, statement B is true. John killed the deer entails, or requires, that the deer is dead, while John shot the deer does not. Presuppositions are statements that are assumed to be true. John realizes that it is raining presupposes that it is raining. Mary regretted that her brother caused a lot of trouble presupposes that Mary has a brother and that he caused a lot of trouble.
Meanings are sometimes “packed” into words. For example, English divides the color spectrum into 11 basic color words. But Dani, a language of New Guinea, has only two color words which, roughly translated, mean dark and light. Comparative lexicology examines the vocabularies of different languages to learn how meanings are packed into words.
