The use of 'the' for classifying

3.19.1 Three ways of making general statements: 'the', zero, 'a/an'

1 With the + singular:

The cobra is dangerous, (a certain class of snakes as distinct from other classes, such as the grass snake)

2 With zero + plural:

Cobras are dangerous, (the whole class: all the creatures with the characteristics of snakes called cobras)

3 With a/an + singular:

A cobra is a very poisonous snake, (a cobra as an example of a class of reptile known as snake)

3.19.2 The group as a whole: 'the' + nationality adjective [> App 49]

Some nationality adjectives, particularly those ending in -ch, -sh and -ese are used after the when we wish to refer to 'the group as a whole': e.g. The British = The British people in general. However, we cannot say 'many British* or 'those two British*, etc. Plural nationality nouns can be used with the or the zero article to refer to the group as a whole: the Americans or Americans; or with numbers or quantifiers like some and many to refer to individuals: two Americans, some Americans:

The British and the Americans have been allies for a long time.

The Japanese admire the traditions of the Chinese For the use of the + adjective {the young, the old, etc.) [> 6.12.2].

3.19.3 The group as a whole: 'the' + plural names [compare > 3.22]
The + plural name can refer to 'the group as a whole':
Families: The Price sisters have opened a boutique.
'Races': The Europeans are a long way from political unity.
Politics: The Liberals want electoral reform

Titles beginning with the axe given to particular groups to emphasize their identity: e.g. the Beatles, the Jesuits.

3.19.4 Specified groups: 'the' + collective noun or plural countable

We can make general statements about specified groups with the + collective nouns, such as the police, the public [> 2.28.2, 2.29]: This new increase in fares won't please the public

The definite article, 'the'

Many plural countables can be used in a collective sense in the same way when particular groups are picked out from the rest of the human community: e.g.ihe bosses, the unions [compare > 2.28.1]: Getting the unions and the bosses to agree isn't easy