Halliday & Matthiessen (1999: 509):
Meaning can be thought of (and was thought of by Saussure) as just a kind of social value; but it is value in a significantly different sense — value that is construed symbolically. Meaning can only be construed symbolically, because it is intrinsically paradigmatic, as Saussure understood and built in to his own definition of valeur. Semiotic systems are social systems where value has been further transformed into meaning.