Nevertheless a denotational inclusion is no more than a suggestion that the concepts might be related by additional restrictions. For instance, the fact that the class of 'portable video recorders' is included in the set of 'things made in Japan' (supposing it were true) does not imply that the meaning of portable video recorder is [Made-in-Japan.X]; we could easily start making some in Thailand and they would still be portable

O' D

It does follow, however, that if two words or expressions have the same meaning, they must have the same denotations, so if we can show a difference in denotations, i.e. if there is something that is one but not the other, then the expressions cannot be synonymous. This is all obvious in some sense, but unless it is stated clearly, the relationships can provide some confusion.