Why do we say “open” and “closed”? Why is one in present tense and the other in past tense?

Question

Edit: to clarify, I mean when shops have a sign that says “open” versus “closed”. Why is it not “opened/closed” or “open/close”?

In: Other

Answer 1

Set X is open. Set Y is closed. Both are present tense because that instance of “closed” is an adjective, not a past participle. You would never say that set Z *was* closed.