What is the difference between "or" and "either...or"?

Question

What is the difference between "or" and "either...or?

Obviously, one comprises one phonological word and the other comprises two. I have yet to find an analysis of "either...or" in which "either" is considered to be an adverb. The Summer Institute of Linguistics glossary of linguistic terms indicates that "either...or" is a correlative conjunction, which the SIL defines as "either of a pair of coordinating conjunctions used in ordered fashion." (See http://www-01.sil.org/linguistics/GlossaryOflinguisticTerms/WhatIsACorrelativeConjunction.htm ) I'm not sure that this definition makes sense for English, because "either" is not a coordinator by itself AFAIK. This definition may apply to other languages. But I've been having a hard time finding examples on the Internet.

Anyway, my chief interest is in the semantic difference between "or" and "either...or". Although I'm asking about two English coordinators, I believe that this question is appropriate for this list because other languages also have a similar contrast.

Because I'm a monolingual English speaker, examples of sentences in which "or" would be acceptable but "either...or" would not be--and vice versa--would be helpful.

Answer 1

Both...And, Either...Or, and Neither...Nor are the classic examples of correlative conjunctions.
Either is a disjunctive dual form in English, parallel with both, a conjunctive dual form, in some uses:

• He wants to talk to both Bill and Mike ~ He wants to talk to Bill and Mike.
• He wants to talk to either Bill or Mike ~ He wants to talk to Bill or Mike.

Outside of dual reference, however, both and either don't work as correlatives:

• *He wants to talk to both Bill, Mike, and Joe. ~ He wants to talk to Bill, Mike, and Joe.
• *He wants to talk to either Bill, Mike, or Joe. ~ He wants to talk to Bill, Mike, or Joe.

Both and either can be used pronominally

• He wants to talk to both (of them).
• He wants to talk to either (one) (of them).

Though only both (as the suppletive dual of the quantifier all) can undergo Q-Float:

• He wants to talk to both/all (of them). ~ He wants to talk to them both/all.
• Both/All (of them) want to talk to him. ~ They both/all want to talk to him.

In general, I think it's most useful to consider either as an auxiliary conjunction; it does some of the work of a conjunction, and appears in an optional supporting role with other conjunctions in special circumstances. That's pretty much what all auxiliaries do in English -- be, get, have, can; articles, particles, and prepositions. Why not conjunctions?

Answer 2

I'm not an expert on this topic but these are some of the most relevant works:

• Den Dikken, Marcel. 2006. Either-float and the syntax of co-or-dination. Natural Language and Linguistic Theory 24(3). 689–749. http://dx.doi.org/10.1007/s11049-005-2503-0.
• Johannessen, Janne Bondi. 2005. The syntax of correlative adverbs. Lingua 115(4). 419–443. http://dx.doi.org/10.1016/j.lingua.2003.09.009.
• Larson, Richard K. 1985. On the syntax of disjunction scope. Natural Language and Linguistic Theory 3(2). 217–264. http://dx.doi.org/10.1007/BF00133841.
• Schwarz, Bernhard. 1999. On the syntax of either ... or. Natural Language and Linguistic Theory 17(2). 339–370. http://dx.doi.org/10.1023/A:1006046306942.

As usual, you can find more relevant literature on the topic by perusing the bibliographies of these works and/or exploring via Google Scholar who has been citing them. Larson and Schwarz are the pivotal contributions. Johannessen gives a fairly non-technical cross-linguistic perspective.

Answer 3

The semantic difference between x or y and either x or y is that either... suggests exclusion of both x and y.

Let me illustrate this with a rough quote from the TV series The West Wing where a character is asked questions about his ex-wife and her pregnancy:

Q: How pregnant is your ex-wife?

A: How pregnant? As I understand it, pregnancy is a binary state, you either are pregnant or you're not.

Either x or y suggests that x and y cannot both be true. You cannot be both pregnant and not pregnant at the same time. x or y allows that both x and y are true.

If you offer someone banana juice or apply juice they can answer Can I have both?

If you say You can have either banana or apple juice they could still be cheeky and say Can I have both?, but they will know that this is not the desired answer.

To be sure, or might be used without either when the context implies that not both x and y can be true:

Q: When will you get your hair cut? A: I'll do it tomorrow or the day after.

Getting one's hair cut is an action that in all likelihood is completed in less than one day. Because this is implied by the context and because it is not important here that the action cannot take place on both days either can be omitted.

The account of either ... or as exclusive that I've given here is supported by the Comprehensive Grammar of the English Language by Randolph Quirk et al., one of the standard academic descriptive reference grammars of the English language (§13.34):

Either ... or emphasises the EXCLUSIVE meaning of or.

However, there are exceptions, for example either live or work in X, in legal usage, appears to mean work or live or both in X.

There is also a question and good discussion of this question son SE English L&U.

Answer 4

In my opinion, Either or means one of them is sufficient.
Or only means both have to be taken into account.