English recognizes a basic distinction of things into two semantic categories: (1) discrete, and therefore countable, realized as ʻcount nounsʼ; (2) continous, and therefore uncountable, realized as ʻmass nounsʼ […] Mass nouns are grouped with singular count nouns […] Typically what the distinction means is not that a mass noun is something that cannot be enumerated, but that if it is enumerated it is by kinds rather than by units [...] Otherwise, if a ʻmassʼ noun is to be itemized, it has to be measured out.
- Halliday (1985), a pag.168