In computer science, particularly in human-computer interaction, presentation semantics specify how a particular piece of a formal language is represented in a distinguished manner accessible to human senses, usually human vision. For example, saying that <bold> ... </bold> must render the text between these constructs using some bold typeface is a specification of presentation semantics for that syntax. An example of interactive presentation semantics is defining the expected behavior of a hypertext link on a suitable syntax.
Many markup languages like HTML, CSS, DSSSL, XSL-FO or troff have presentation semantics, but others like XML, XLink and XPath do not. Character encoding standards like Unicode also have presentation semantics. One of the main goals of style sheet languages like CSS is to separate the syntax used to define structured data from the syntax endowed with presentation semantics that is used to render the data in various ways.