If the subject of a sentence is separated by "and/or", should the verb be pluralized, as with "and", or agree with the rightmost subject, as with "or"? For example:

His co-workers and/or his boss was at fault.


His co-workers and/or his boss were at fault.

  • tchrist gives the standard answer in his comment below. One is assuming, of course, that the and/or construction itself is 'allowable', and I'm fairly sure I've read pundits saying it isn't. Like tchrist, I'd use the 'proximity' rule here, conceding that there's no logically correct answer (without a lengthy rewrite: His co-workers were at fault, his boss was at fault, or they were all at fault.) Commented Nov 9, 2013 at 23:35
  • Here: owl.english.purdue.edu/owl/resource/599/01
    – Pacerier
    Commented Jul 29, 2017 at 9:32

5 Answers 5


I checked online to see how other interested parties have come out on this question. Grammar Girl votes for consistently treating the combined subject as plural:

If you feel you must use "and/or," my nonscientific survey of professional writing shows that you probably want to treat "and/or" as though it makes the subject plural. For example, Kelly's sentence would read

This message and/or attachments are confidential.

I must say, though, that I don't see how you could come to that conclusion and not insist that the construction requires an explicit "these" after the "and/or" conjunction:

This message and/or these attachments are confidential.

In contrast, Grammar Logs seems to focus on the fact that the final element in the combined "and/or" conjunction is or, meaning (as I read it) that the verb should match the number of the second element in the "and/or" pair, just as if the conjunction were simply or by itself:

Every grammar reference book I own warns against the use of this legalistic construction, and your quandary is another good reason to avoid its use. You can almost always substitute a simple "or" in its place or rewrite the sentence for greater clarity. I can't find an authoritative answer for you (if you insist on using the "and/or" construction), but I think I would treat this amorphous conjunction as a kind of or and base my choice on that.

Before proceeding further, I should note that the OP's "and/or" question presents us with two levels of complication: On one level, it poses the question of whether the plural noun before the "and/or" or the singular noun after the "and/or" should control the number of the following verb. But on a second level, it raises the issue of whether any pair of nouns sandwiching "and/or" should ever be followed by a singular verb.

The discussion at Word Reference Forums illustrates this second problem:


The president and/or the vice president makes the decision.

The proofreading function of my Word says "makes" should be "make". But I think it should be "makes" because the verb must agree with "the vice president". (In this case, the president and the vice president are different people.) Am I wrong?

In other words, the WRF poster's Word program seeks to enforce a rule under which the presence of and in "and/or" automatically defines the subject as plural—even though the nouns on both sides of "and/or" are singular. This seems to be the rationale behind Grammar Girl's answer, too.

The most interesting response to this question in the comment string that follows points to the following discussion at Grammar-Monster.com of the conflicting rules governing either/or statements that include a plural element. The writer at Grammar-Monster identifies the first of these two approaches as the "standard convention":

If the pairings either/or (often the either is omitted) or neither/nor form part of the subject of a verb and at least one of the elements is plural, then the verb must be plural too.

Under this rule, " Either the budgies or the cat has to go" is incorrect. The second approach, according to Grammar-Monster, is the "proximity rule":

Not all grammar conventions agree with the ruling above. In fact, there is notable leniency on whether to use a plural or singular verb when one of the elements is plural. Under the proximity rule, the verb is governed by the element nearest to it.

Under this rule, " Either crumpets or cake are sufficient" is incorrect.

In the United States, the "proximity rule" is the more common style recommendation (which makes Grammar-Monster's "standard convention" the nonstandard convention in the U.S.). For instance, Words Into Type, Third Edition (1974) offers this guideline:

Plural and singular substantives joined by "or" or "nor." When a subject is composed of both plural and singular substantives joined by or or nor, the verb should agree with the nearer.

[Example] Others are trapped by the fear that their interests or their property is being threated.

The proximity rule is the rule I was taught, and it would certainly seem to point to a singular verb in the OP's sentence if that sentence were spelled out at full length as follows:

Both his co-workers and his boss or either his co-workers or his boss was at fault.

This awkward-sounding rendering of the sentence amounts to translating "X and/or Y" as "(X and Y) or (X or Y)"—that is, as a conjunctive "X and Y" and a disjunctive "X or Y" nested in a larger disjunctive statement that we might express as "Either (X and Y) or (X or Y) considered as two pairs of exclusive alternatives." But as some of the commenters at Word Reference Forums seem to suggest, it is possible to interpret "and/or" inclusively, as meaning "either or both of X and Y," in which case the "X and Y" would seem to command a plural verb, regardless of whether the specific match for the condition happens to come from "either of X and Y" or from "both of X and Y"—and regardless of whether X and Y are both singular, both plural, or one singular and one plural.

I have no idea which of the conflicting rules—"standard convention" or "proximity rule"—will win out as the dominant way to handle "and/or" in the future. The "and/or" conjunction seems to be in no danger of fading away; and if it is here to stay, publishers need to come up with a consistent approach to handling it if they want to avoid distracting readers from the actual content of their authors' prose whenever a problematic "X and/or Y [+ verb]" construction arises.

In the near term, though, I think that the "X and/or Y [+ verb]" construction is inescapably distracting—at least when the verb is number specific—and I wouldn't use it. To avoid that construction here, I would express the idea embedded in the OP's example along these lines:

Either his co-workers and his boss were jointly at fault, or one or the other of the two was entirely to blame.

  • "This message and/or attachments are confidential" is hardly fair. What if you use singular on both sides?: "This message and/or the attachment is confidential".
    – Pacerier
    Commented Jul 29, 2017 at 9:26

Though I do not present a general method of deciding the nature of the verb, one case is particularly worth mentioning:

Sometimes it is the sense of the subject(s) joined by and that matters. For example, the first sentence below refers to the same person who was a writer and a musician, while the second refers to two different persons, one a writer and other a musician. The verb is set accordingly.

  1. The writer and musician has arrived.
  2. The writer and the musician have arrived.

With or, the following action denoted by the verb applies to only one of the subjects joined by or, though the sentence does not specify which. Hence use of singular is justified.


'A and/or B' is logically equivalent to 'A or B or both'. Since 'both' is always plural in this context, you can't go wrong with the plural verb, as in

His co-workers or his boss or both were at fault.


His co-workers and/or his boss were at fault.

  • 1
    You would actually say, "He and/or she are going to win." instead of "He and/or she is going to win." when both conjugands are singular? Commented May 2, 2014 at 2:38
  • If you meant "He or she or both are going to win", yes.
    – JK2
    Commented May 2, 2014 at 3:11
  • Obviously that is what the and/or indicates. So I meant that. I think that phrasing would bother a lot of people. Again, it cannot be wrong, because this is unmapped territory, but it just sounds alien. Commented May 2, 2014 at 3:25
  • That's probably because the "or she" part makes the whole package sound singular, when in fact the unusual coordinator "and/or" makes the whole package sound plural at least logically. And the question is whether you should go with the superficiality or the logic when it comes to the subject-verb agreement.
    – JK2
    Commented May 2, 2014 at 6:40
  • You should definitely not go with the logic. This is English, after all. Commented May 3, 2014 at 19:45

Rule 1: Subjects joined by "and" are plural.

Rule 2: For subjects joined by "or", look at the subject closest to the verb.

Rule 3: For and/or or or/and, use the second conjunction in time.

Example/Explanation of Rule 3:

Saying "Sam and/or Sarah (is/are)"

is the equivalent of saying

"Both Sam and Sarah or either Sam or Sarah (is/are)"

The "/" is the functional equivalent of "or" requiring us to look at the compound subject closest to the verb. Which ultimately means that we use whatever the second conjunction in time is.

Applied to your sentence:

It is the equivalent of saying, "Both his coworkers and his boss or either his coworkers or his boss (was/were) to blame.

The or requires us to apply the compound subject closest to the verb:

"Either his coworkers or his boss (was/were) to blame."

Since "his boss" is closest to the verb, we say ,"Either his coworkers or his boss was to blame.


Simply use the last conjunction in time to get the same result as above:

"Either his coworkers and/or his boss (was/were) to blame."

means that we are looking at "boss", which means that we are using the singular "was".

"Either his coworkers and/or his boss (was/were) to blame."

  • @JonJayObermark If I were to list every single exception to every single rule, my page would be three to four times as long. Further, you mean one composite "subject"--'object' has a very different meaning in the subject-verb agreement discussion we are having right now. Finally, your comment is not applicable to the question at hand while my rule is. Thank you for your inanity. Here is a link from the University of Wisconsin if you need to brush up on your rules: writing.wisc.edu/Handbook/SubjectVerb.html Commented May 5, 2014 at 21:43
  • @JonJayObermark Wait, what you said applied to the question? If so, you are right. If not, why did you say it? Snipe less. Commented May 5, 2014 at 22:06
  • OK, I will delete the comment. And in the future I will do my very best to ignore you as much as possible. Commented May 5, 2014 at 22:10

Go with the element closest to the verb, as is common for 'or'.

People do this for 'and' in colloquially speech anyway. So they will hear it better than if you inflexibly enforced the formal rule for 'and', which often sounds stilted to native speakers already.

In your case, take the singular, from 'his boss'. But if the two were reversed, I would have gone with the plural from 'co-workers'.

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