The study of the meaning of words. A semantic vocabulary is a formal description of the data used in a specific domain such as advertising, physics, real estate, telecom, etc. Contrast with
syntax, which governs the structure of a language and the rules pertaining to the actual data. For example, a semantic tag for temperature may be Fahrenheit, but the syntactic values for Fahrenheit may be numeric -60 to +120. The statement
a = b may be syntactically correct, but if there is no "a" or no "b" defined elsewhere, the code is semantically invalid. See
Semantic Web,
semantic error and
Systemantics.
A Note from the Author
Obviously, a dictionary of terminology is all about semantics, and researching countless articles to be able to define an IT topic is an exploration in semantics. In this field, people love to use different words for the same subject (for extreme examples, look up
USB drives and
digital media hub terminology). But even in the field of semantic data (Semantic Web, linked data, ontological vocabularies, etc.), the terminology is just as bad, if not worse. This is one area where people might think about uniform semantics while they're writing about it. It has been a bit of a "semantic nightmare" researching articles about the Semantic Web.