Grammar question about articles.

This is how I would write the following:

Mr. Cook bought us our choice of tea or coffee or Mr. Cook bought each of us a cup of tea or coffee.
A horse is long and so is its hair.
A username and password are required to log into the website. (The second “a” is unnecessary.)
Is it a good or bad thing? or “Is it a good thing or bad thing?* Both are correct but the latter is slightly more emphatic. (Again, the second “a” is unnecessary.)

There are definitely rules to usage of articles with conjunctions but to a great extent it’s always also a writer’s choice as how to best convey his or her intent and meaning. Good writing is more about clear communication that following ironclad rules.

I love this small grammar book. It’s always served me well.

Is it a good thing or a bad thing?
Two occurrences of “thing”, so two occurrences of the article “a” as well.

Is it a good, or a bad thing?
-> This is the same sentence, but the first occurrence of “thing” has dropped out. The article stays behind though.

In this case both forms should be allowed, but my preference would be the second with two occurrences of the article “a”. The world seems to prefer that sentence as well, with 996000 hits in google, versus 35800o with onluy one occurence of “a”.

A horse and his (its) hair.
This time there are still two determiners: one in the form of an article (A) and one in the form of a possessive determiner.

In general, you should watch for the meaning of what you want to convey.

You need a username and password (combination).
You need a username and a password. Implies it could be any password.

You need a man and a horse. (Any man, any horse).

One of the nice things about English is that you are seldom restricted to saying a thing in a very particular way. It’s an informal language as far as general sentence structure; sentences can nearly always be recast to remove ambiguity, to improve readability and understanding, to change meter and rhythm, even.

For example, in your first sentence:
Mr. Cook bought us a cup of tea and a cup of coffee.
You can say:
Mr. Cook brought us tea and coffee, a cup of each.
Mr. Cook brought us a cup each of coffee and tea. Or just
Mr. Cook brought us cups of coffee and tea.

There is absolutely nothing wrong with your starting sentence, either, unless you like to compress it, as I prefer.

You get to write the sentence you want that expresses as much or as little detail as you want, but some sentences are clearer than others – and sometimes trying to put too much detail into a sentence almost automatically makes it more awkward. That’s the downside.

I’m staying away from the horse and hair thing; it just seems odd to me to compare the length of a horse, which may be 2 meters or more, with its hair, which is going to be under a meter in any case. The proportions don’t match. I simply wouldn’t write that sentence or make that comparison. I don’t think it can be done in a meaningful and sensible way.

Since usernames and passwords usually go together, in the particular case of computer / website usage my own preference is to shortcut the usage with the word “account”, which can be specifically clarified to state “username” and “password”, so:
A username / password account will be required to log into the website. Otherwise,
“A username and password are required to log into the website,” is fine.

Is it a good or a bad thing VS Is it a good or bad thing.
I’d avoid this usage in most cases, because the “thing” is probably not a physical item, is it? (I’d also be more likely to express an opinion, and then request agreement or rebuttal.) So I’d try for something like:
Is this a good or bad idea? Is this a good or bad plan?
I’d be more apt to say:
I think this is a good plan. How can it be improved? Or:
I do not like this plan for the following reasons… (to be listed). Here is my alternative. (Which is implied, at least in my own opinion, as “better”.)

“Mr. Cook bought us a cup of tea and a cup of coffee.”

You cannot remove either “a” in this case, without rewriting the sentence as in the examples given by @Pachyderm_In_The_Room. You could also write it as:

“Mr. Cook brought us cups of tea and coffee”

However, in re-writing the sentence, you lose information about the number of cups brought, and what was in each cup. Before, there were definitely two, and one was coffee, the other tea. Now there might be any number of cups, and we don’t know what was in each cup.

“A horse and his hair is long.”

First, you must use “its hair” because “his” is reserved for people. Second, because “long” is describing two things (horse + hair), you must use the plural: _“A horse and its hair are long. You could, rather poetically, say “Horse and hair are long.” But it’s not a common way of expressing the idea.

“A username and password is required in order to log in to the website.”
A username and a password is required in order to log in to the website.”

Again, here you are adding two subjects together (username + password), so the verb must be plural:

“A username and password are required in order to log in to the website.” or
“A username and a password are required in order to log in to the website.”

As to whether or not to include the “a”, both versions are acceptable and neither one is preferred over the other.

For your last example, either
“Is it a good or a bad thing” or
“Is it a good or bad thing”

Here, it would be less awkward to say, as in your other examples, either:
“Is it a good thing or a bad thing?” or
“Is it a good or bad thing?”

So, to answer your question, there is no hard and fast rule about whether to include the article with both items in the sentence – sometimes it sounds right, sometimes it sounds awkward. But watch your tenses: if you are using “and” to add together subjects of the same verb, that verb must become plural. If you are using “or” to denote one or the other, the verb remains singular, because only one of the options is the subject of the verb.

@glacial, @@Pachyderm_In_The_Room, @glacial @CWOTUS @whitenoise :

Thanks for the answers. I think the example of horse I gave is not correct and it does not clear the question I have. The following examples I found have two subjects and those are related to one thing.

1. The novelist and poet is dead. (I think the person who was a novelist as well as poet is dead and it takes a singular verb.)

2. Honor and glory is his reward. (ditto #1.)

Once again, thank you for the helpful answers.

1. “The novelist and poet is dead”
In this case, the sentence is describing one person who is dead. You could say:

“The novelist and the poet is dead”, but this would sound awkward, to the point that the reader might think that you meant to say:

“The novelist and the poet are dead” which would mean that two people are dead: one a novelist, the other a poet.

2. “Honor and glory is his reward.” As in the examples which I gave above, this sentence is incorrect. Because you are adding two subjects together (honor + glory), you must use the plural:

“Honor and glory are his rewards”.

I’m not sure how sentence 2 relates to your question about articles, though. It would be correct to say either “The honor and glory are his rewards” or “The honor and the glory are his rewards”, but it would more commonly be written without any articles.

I am not sure whether the honor and glory sentence should be singular or plural. The two terms are so often mentioned together that I think it can be looked at as a single package, like fame and fortune or bacon and eggs. You would not say bacon and eggs are being served.

@LostInParadise o_O

If you would not… you really should.

@glacial

No you shouldnt. Bacon and egss isn’t plural… it’s a single dish.

Like rice technically is plural but used as a singular noun.