It strikes me that almost always using all four adjectives "open/closed" and "undone/done" for all the words "button", "zipper", "fly" and "zip" can be used interchangeably and freely; but I need to make sure about it!
E.g.
- Your (zipper / button / fly / zip) is undone/open.
- Your (zipper / button / fly / zip) is done/closed.
Is there some fixed terms about it in English or depending on personal preference one can use each one of them?
In US usage, at least in my experience, one simply does not say that a zipper or button or fly is "undone", still less that it is "done". One says that it is open or closed, or more formally but far less commonly, that it is fastened or unfastened. I have read uses of "undone" in BrE to mean open, but I don't recall encountering 'done" to mean closed.
I think a button is far more likely to be describes as "unfastened" than a zipper is, the zipper will almost always be refereed to as "open" instead.
Also, the use of "zip" as short for "zipper" is very rare in AmE, in my experience.
"Done" doesn't really mean "closed" in the context of dressing; rather it implies completion.
You expect someone wearing trousers to close their fly, so once they do that, the zipper is done. The reverse is to undo it.
We also use the same expressions with buttons. If you put a button into an eyelet, the button is done. We idiomatically say "I have done up the buttons". If a button pops out of the eyelet we say "it has come undone", or if we deliberately unfasten it then "I have undone the button". It is not common to say open or close about a button - we would say "fasten/unfasten".
Other items of clothing about which one might say done/undone include neck ties and shoelaces. Otherwise one would say "tied/untied" about both of these.
