In these examples the… doesn’t mean one particular thing. The rose = roses in general, the giraffe = giraffes in general. We use the + a singular countable noun in this way to talk about a type of plant, animal, etc. Note that you can also use a plural noun without the:

B.
The + adjective

We use the with some adjectives (without a noun). The meaning is always plural. For example, the rich = rich people in general:

We use the especially with these adjectives:

the rich the old the blind the sick the disabled the injured

the poor the young the deaf the dead the unemployed the homeless

These expressions are always plural. You cannot say “a blind” or “an unemployed.” You have to say “a blind man,” “an unemployed woman,” etc.

C.
The + nationality words

You can use the with some nationality adjectives when you mean “the people of that country.” For example:

You can use the in this way with these nationality words:

the British the Welsh the Spanish the Dutch

the English the Irish the French the Swiss

You can also use the with nationality words ending in -ese (the Japanese / the Chinese, etc.). With other nationalities you have to use a plural noun ending in -s:

(the) Russians (the) Italians (the) Arabs (the) Germans (the) Turks

For the see also Units 67, 68, and 70, 71, 72, 73.