Theoretical Grammar

The definitizing function

The object or thing denoted by the noun is presented as a part of some complex. In modern science the term “frame” is often used. The frame is a structurally organized system of images. For example, the frame “classroom” includes a window, a blackboard and a door. So if both the speaker and the hearer know what classroom they are speaking of, the constituents of the classroom don’t need any special concretization, and the indefinite article will be used.
e.g. I want to talk to the rector (even if you have never met the man).

3. 
   The individualizing function
   

The object in question may be presented as a unique thing with the hearer’s attention focused on its distinguishing features, which are represented with the help of a particularizing attribute. The object is singled out from the class it belongs to. The particularizing attribute can be expressed by:
a) adjectives in the superlative degree
e.g. This is the easiest way out.
b) ordinal numerals
e.g. I have forgotten the first word.
c) attributive relative restrictive clauses
e.g. I need the book I bought yesterday.

FUNCTIONS OF THE ZERO ARTICLE

In most cases the zero article performs the same functions as the indefinite one. The difference is that the combinability of the latter is restricted to the group of countable nouns used in the singular form, whereas the zero article combines with uncountable nouns and countable nouns in the plural.
e.g. It was a large room with many windows.
The toasts were in champagne.
Still there are situations where the zero article is used in its specific functions which are different from those of the indefinite article. When used with the zero article, the noun loses its general grammatical meaning of thingness to a certain degree and acquires the meaning of qualitativeness. For example, the nouns “day” and “night” used with the zero article stand for “light” and “darkness” rather than time units.
Theoretical Grammar
Kolomiytseva O.A.