[...] In the identifying mode, the meaning is ʻ 'a' serves to define the identity of 'x' ʼ. Here 'a' and 'x' are two distinct entities, one that is to be identified, and another that identifies it [ Identified and Identifier] [...] In the most general terms the Identifier fixes the identity of the target element [Identified] in one of two ways: either by specifying its form, how it is recognized, or by specifying its function, how it is valued.
- Halliday (1985), a pag.115