I'm reading a book which represents sentences of two languages in parallel. I've noticed that one of the sentences is:

When does the museum open?

My question is: Is it not supposed to be with a different type of auxiliary verb (be) rather than the auxiliary verb do - as in the following?

When is the museum open?

...since open is an adjective in this context.

The word open is used to be used in this context as an adverb. Always when I listen to people who talk about the work times of places they say: it IS open between such hour to such hour. I've never heard that someone said "it opens between..." and used it as a verb. Maybe I'm mistaken and it is in use as verb in such context in native English spoken countries.


  • Ah! I understand. No, open is a verb, not an adjective. The declarative form of the wh-question is: The museum does open when. Commented Oct 30, 2016 at 2:25
  • Have you used a dictionary to learn about the verb to open? "When do you open the store? "It opens sometime between 8:00 and 9:00." Commented Oct 30, 2016 at 2:33
  • Yes, I have. Before I asked my question I knew that it can be a verb or an adjective, but this is not the point. The point is that which one of them is used to be in the context that I represented. I edited my question and maybe it will make my question clearer. Commented Oct 30, 2016 at 2:35
  • The two sentences are different. We say "The museum opens at 9 o'clock" (verb to open) and "The museum is open at 9 o'clock." (open is an adjective and complement of the copula.) Either one is fine, although the former is more idiomatic in the declarative. In the interrogative, we would usually use the does form. Commented Oct 30, 2016 at 2:38
  • 1
    He is confused because the inanimate thing produces an action, right?But that exists in any language, clocks strike, buses go and doors open.
    – V.V.
    Commented Oct 30, 2016 at 5:04

2 Answers 2


In the sentence, "When is the museum open," the word "open" acts as an adjective.

Whereas in the sentence, "When does the museum open," the word "open" acts as a verb.

The first sentence would be used when you want to know the time frame of when the store is available for business (The store is open 6am to 7pm).

The second sentence is used to ask what time the store opens its doors; this would be answered with a specific point in time, not a range of times (The store opens at 9).


I would use the first form if waiting to get in

Me: When does the museum open?
Them: In 25 minutes.

I would use the second form when planning future travel.

Me: When is the museum open?
Them: 9 a.m. to 5 p.m. Mondays through Fridays except bank holidays.

To me the first form is suggestive of an event (opening) and the second is suggestive of a state (being open), hence the subtle connotation.

But really there isn't a lot of difference and the other party will work out what you mean by context.

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