adjective/pronoun

[hanuman_2000]

Sir,

1.All trees are green.


In this sentence the word "all' is an adjective. is it ok?

2.All the trees are green.

3.All of the trees are green.

I am not able to understand the differences between (2) and (3).

Please explain a bit.
Thanks.

[Alan]

1. Correct (a determinative adjective).
2. is merely an ellipsis of 3, in which 'all' is a pronoun. Some linguists, however, prefer to term the 'all' of 2 a 'predeterminer'.