Neither is or neither are

Yes, you would use is unless they were grouped together to create a plural. dariensan said it right. If it was "vodka and rum can be used", then the correct sentence would have read "For this recipe, both vodka and rum can be used, though neither are ideal." Note that the "both" is not required, but I added it out of personal preference as I find that it sounds better in such a context. However, if the sentence were to use "none of them" instead of "neither", it would not matter if "and" or "or" were used. For example, "For this recipe, vodka or rum can be used, though none of them are ideal." This is because the word "them" is plural. However, I would doubt you would find that on a well written recipe or any professionally made document, because while it is not necessarily incorrect grammar, it sounds wordy and strange. Neither is a much better word choice of course.

Also, if the recipe items themselves were plural, you would use "are" after neither regardless of "and" or "or". Since I cannot think of the plural for vodka or rum, let's say something like "For this recipe, apples or oranges can be used, though neither are ideal." Notice the use of "or" but since the fruits themselves are plural, "are" would still be required. To say "neither is" would be incorrect, unless the sentence read "For this recipe, an apple or an orange can be used, though neither is ideal."

So what do you do when one is plural and the other is not?

e.g., "Two small apples or one large apple can be used, though neither is/are ideal"

I have to respectfully disagree with a couple of you. As used in the sample sentence, "neither" unquestionably takes the singular. Think of it as being short for "neither one". "Neither one is ideal" is the only correct form.

Believe it or not, this is actually a rule, and therefore to be cherished for its rarity.

Whoops, forgot. Jun-Dai Bates-Kobash asked what you do when one element is plural and the other is not: "Two small apples or one large apple can be used, though neither is/are ideal"

The answer is that "neither [one]" still takes a singular verb.

"Neither" means that given two choices, both are to be individually rejected. Therefore a singular verb is required. If you want to refer to the duo and reject them, you should say something like "both are not".

Pretty much "what Teresa said"

My high school english teacher taught us a little cheer: "each, either, neither, the bodies and the ones!" (it's important to say it like a cheer). :) By "the bodies," he meant somebody, anybody, etc and by "the ones" he meant anyone, someone, noone, etc. These are all words which precede singular verb conjugations. In the sentence "neither of the boys IS going to the game," one is implied after neither and so the verb is singular.

"Neither" can be singular or plural, depending on what it refers to. ("Neither the teachers nor the administration are being reasonable in these negotiations"; "neither the teacher nor the dean is being reasonable in these negotiations.") "Vodka" and "rum" are singular; hence the choice is one singular thing or another; hence the "is." -- BTW, often, when in doubt, one can take the coward's way out and say "neither would be ideal." No agreement to deal with.

I think the issue is that your casting is not right. In the case mentioned, it's not that "both are not ideal", but rather "neither one is ideal."

If neither is ideal, why would either of them be mentioned in the recipe? To illustrate my point: "For coconut cream pie, ground beef or ceramic tiles can be used, though neither is ideal."

While grammar is important, one should place a higher importance on the overall meaningfulness of the sentence to begin with.

In this case, the author should have replaced this clumsy sentence with:

"Ideally this recipe calls for GIN, however, you may substitute with rum or vodka."

Neither is always singular.

No one has gotten the general rule right yet. "Either" and "neither" take a singular verb in some cases and a plural verb in others, as follows:

1. We start with the general rule for compound subjects separated by "or":
If both subjects are singular, use the singular verb:
Harry Harmer or Jane Jones is coming to visit tomorrow.

If both subjects are plural, use the plural verb:
The Harmers or the Joneses are coming to visit tomorrow.

If one subject is singular and one is plural, the verb form agrees with the subject closest to the verb:
The Harmers or Jane Jones is coming to visit tomorrow **NOTE: CORRECT, BUT AWKWARD AND DISFAVORED**
Jane Jones or the Harmers are coming to visit tomorrow **PREFERRED**

2. It's the same if we add "Either" to the front of the sentence:
EIther Harry Harmer or Jane Jones is coming to visit tomorrow.
Either the Harmers or the Joneses are coming to visit tomorrow.
EIther the Harmers or Jane Jones is coming to visit tomorrow. **CORRECT BUT AWKWARD**
EIther Jane Jones or the Harmers are coming to visit tomorrow. **PREFERRED**

3. FInally, it's the same if we substitute "neither" and "nor" for "either" and "or":
Neither Harry Harmer nor Jane Jones is coming to visit tomorrow.
Neither the Harmers nor the Joneses are coming to visit tomorrow.
NeIther the Harmers nor Jane Jones is coming to visit tomorrow. **CORRECT BUT AWKWARD**
Neither Jane Jones nor the Harmers are coming to visit tomorrow. **PREFERRED**

Yes, in your example, you use the singular, because what you really means is "neither vodka nor rum is ideal." But if you replace vodka and rum with "doughnuts" and "cookies," then you would use "are."

Saying "both are not ideal" would be a bad mistake, because it is ambiguous. Do you mean "neither vodka nor rum is ideal"? Then say "neither one is ideal." Or do you mean "Using both vodka and rum together is not ideal"? In that case, say "using both together is not ideal."

As you can tell, I'm a lawyer. Who else would actually LIKE this stuff?

Cheers,
Mike