Fowler comments that different fields produce different language, most obviously at the level of vocabulary (Fowler. 1996, 192) The linguist David Crystal points out that Halliday's 'tenor' stands as a roughly equivalent term for 'style', which is a more specific alternative used by linguists to avoid ambiguity (Crystal. 1985, 292). Halliday's third category, "mode", is what he refers to as the symbolic organisation of the situation. Downes recognises two distinct aspects within the category of mode and suggests that not only does it describe the relation to the medium: written, spoken, and so on, but also describes the genre of the text (Downes. 1998, 316). Halliday refers to genre as pre-coded language, language that has not simply been used before, but that predetermines the selection of textual meanings. The linguist William Downes makes the point that the principal characteristic of register, no matter how peculiar or diverse, is that it is obvious and immediately recognisable (Downes. 1998, 309).