- referentially opaque/transparent
- A distinction between the contexts into which referring expressions can be put. A context is referentially transparent if any two terms referring to the same thing can be substituted in it
*salva veritate*, i.e. without altering the truth or falsity of what is said. A context is referentially opaque when this is not so. Thus, if the number of the planets is nine, then ‘the number of the planets is odd’ has the same truth-value as ‘nine is odd’; whereas ‘necessarily the number of planets is odd’ or ‘*x*knows that the number of planets is odd’ need not have the same truth-value as ‘necessarily nine is odd’ or ‘*x*knows that nine is odd’. So while ‘…is odd’ provides a transparent context, ‘necessarily…is odd’ and ‘*x*knows that…is odd’ do not. See also extension/intension.

*Philosophy dictionary.
Academic.
2011.*