“Every town and city has areas like this.” (source)
When I first came across this clause, I thought it might have wrong verb form of has instead of have. Now I can understand why there is has. But it gives me some other questions. Can a clause, ‘Every town or city has areas like this’, be made under any circumstance? If it’s possible, is the verb form, has, still right?
This is an example of a common thing that people trip over in English. The simple subject of the sentence is not "town and city", which would be plural because there are two of them. The simple subject is "every", which is singular.
"Every" is a bit of a funny word in that way. Even though we use it when talking about many things, it is considered singular, because we are only talking about one of them at a time.
Suppose we said, "Every town has areas like this." Then I think it would be more apparent that the verb should be the singular "has".
If you said, "Towns and cities have areas like this", without the every, then the subject is plural and so you need the plural verb. Or if you said "All towns and cities ..." Again, then it's plural.
Your example:
”Every town and city has areas like this.”
would explicitly read:
Every town and every city has areas like this.
The subject – verb agreement is correct.
Now, let’s consider the general case in which you replaced the conjoining conjunction and with the disjunctive conjunction or.
The pattern would be:
“every A or B +verb”.
In this case a correct subject – verb agreement is given by the form of A and B, whether they are singular or plural. More can be read here
