The definite article is used before a noun to show that the object denoted by the noun is marked as a particular object, distinct from all other objects of the class. That is why the definite article is described as an individualizing article.
When the noun is used with the definite article the context pr the situation pf speech shows that the mind of the speaker is concentrated on that particular object.
Ann is in the garden (=the garden of this house).
He sent for the doctor (== his own doctor).
Please pass the wine (=the wine on the table.).
I'll leave you a message with the secretary (==the secretary of the office, or my secretary).
The noun used with the definite article may have a restrictive attribute which shows that the meaning of the object is restricted to such a degree that it can be easily distinguished from all other objects of the same class.
He saw a familiar face in the second row. Are you sure the man you saw is the prisoner? I can tell you the very moment I fell in love with her. She knew precisely the right moment for doing the right thing. He was well-dressed, the best-dressed man in the room.
Here are the three main cases of the use of the definite article:
(1)It may be used to identify a particular object denoted by the noun. The objects is made definite by the context (very often, though not always, by being mentioned a second time) or, rather, by the situation.
There is a tree in the garden. The tree is an oak. How did you like the film? This is the house that Jack built.
In such cases the definite article retains its demonstrative force, and is used in this meaning more often than the demonstrative pronouns "this" or "that".
Let me have the book. Дайте мне (эту) книгу.
(2) When the noun denotes a unique object,(the earth, the sun, the moon, the universe, the sky, the North Pole, etc.).
Kopernick proved that the Earth goes round the Sun. The Universe is an awfully big place.
(3) When the noun is used in a generic sense, i.e. the object is taken as the type embodying all the characteristic features of the class and, for this reason, denoting the whole class.
The verb is a part of speech denoting an action. The tiger is a big cat-like animal. The book deals with the novel as a genre of epic literature,
Here also belong nouns in the singular and plural denoting social groups and nations: the aristocracy, the bourgeoisie, the proletariat, the workers, the working people, the: Americans, etc.
N o t e that the nouns man and woman in a generic sense are used without any article.
What an optimistic animal man is. Woman is not inferior of man. "Why is woman weaker?" "Because man has done her so." The dog is man's best friend. There is no account for woman's logic.