how to say someone that glass has been used

Question

Here's the situation : A person has already drunk some water from a glass , and i want to say this to some other person . I am having difficulties understanding what will i say to other . Will it be "This glass has been used ".

Answer 1

Yes it’s correct to say:

The glass has been used because the glass was used some time in the past, is still being used now in the present and certainly may remain used in future.

You also may simply say:

The glass is already used or

The glass was already used.

Using past simple express an action finished somewhere in the past which is correct in the context.

As we can see there are many correct possibilities to express this.

Answer 2

You could say that the glass has been used. I would be more inclined to say the glass is dirty.

In this context, "dirty" is understood to mean "should be cleaned before you use it" regardless of the presence of any actual dirt.