A central notion in a theory of morphology is that of the content sign, or morpheme, which can be understood as consisting of a signans (sign vehicle or means), a signatum (sign value or object), and a sign rule establishing the relation between the two. Morphemes vary greatly according to the kinds of signantia, the kinds of signata, and the kinds of signatum-signans relations they comprise.
- Andersen (2004), Pag. 399