€ 10,764.00 = ten thousand seven hundred AND sixty-four euros

£ 12,873.00 = twelve thousand eight hundred AND seventy-three pounds

US$ 13.72 = thirteen dollars (and) seventy two cents or thirteen seventy two

10% = ten percent

1,400 = one thousand four hundred or fourteen hundred

0.7% = nought point seven percent (British English) or zero point seven percent

US$ 480.00 = four hundred eighty dollars

1/2 = a half or one half

1/3 = a third or one third

1/4 = a quarter or one quarter

3/4 = three quarters

4.7 = four point even

6 1/2 = six and a half

562,693,300 = five hundred AND sixty two million six hundred AND ninety three thousand three hundred

We never say 300 = three hundreds

CORRECT is three hundred.

We never say 2000 = two thousands

CORRECT is two thousand

So when you say:

There are seven thousand trees.

The noun trees is countable and plural. thousand is an adjective in this example. Even if you don't say "trees" its still implied.

But you could say:

There are thousands and thousands of trees."

where "thousand" is used as a noun and you are counting groups of 1,000.