 In standard (1-dimensional) possible worlds semantics, the semantic value of an expression is an intension, a function that assigns an extension to the expression “at” every possible world. For instance, the semantic value of a definite description like ‘the best known Swiss citizen’ is a function that takes as input a possible world and yields as output whoever happens to satisfy that description in that world, and the semantic value of a proper name like ‘Roger Federer’ is a constant function that maps every possible world to the very same individual, RF. Such intensions reflect commonsense intuitions about the “modal profile” of the objects, kinds, or properties picked out by our words – i.e. different possible ways those features could be  instantiated.[2]  This framework is also used to explain the meaning of modal operators like ‘necessarily’ and ‘possibly’: a sentence is necessarily true just in case it is true at every possible world, and it is possibly true just in case it is true at some possible world. [See the entries on  intensional logic  and  modal logic.]