What is the conceptual distinction between coordinating conjunctions and subordinating conjunctions?

Question

While it is easy enough to identify coordinating and subordinating conjunctions by memorizing lists of them, the actual distinction seems arbitrary. Coordinating conjunctions are said to join (among other sentence elements) two independent clauses, while subordinating conjunctions are said to join a subordinate clause to an independent clause.

The problem is that it appears to be the very presence of a subordinating conjunction which makes an otherwise-independent clause subordinate. For example, in the sentence...

Stock prices would have plummeted, unless the company issued a public apology.

...the second clause is only subordinate by virtue of including the word "unless." "The company issued a public apology" expresses a complete thought, but "unless the company issued a public apology" does not. So the presence of the word "unless" explains why the second clause is subordinate, which explains why "unless" is a subordinating conjunction.

However, in the sentence...

Stock prices would have plummeted, but the company issued a public apology.

...the same analysis is not applied. Rather, the word "but" is considered to stand between the two clauses, belonging to neither. This grants independent status to the second clause, "the company issued a public apology," whereas if the word "but" were to be included, it would be a subordinate clause, and therefore "but" would be a subordinating conjunction.

A sort of explanatory circularity is apparent, and it's not at all clear to me why "unless" and "but" should be treated differently in these examples. What is so special about the FANBOYS conjunctions that they are said to stand outside of independent clauses, while the rest are said to be part of otherwise-independent clauses, making them subordinate?

Answer 1

The FANBOYS mnenomic has been popular in the teaching of English to native speakers (particularly in the USA using textbooks such as Warriner's English Grammar and Composition). One of the goals of instruction is to help students learn to write correctly constructed and punctuated sentences, and to avoid sentence fragments and run-ons or comma splices.

In such a context it is useful for students to know that they can construct a complete sentence containing one clause beginning with a FANBOY (coordinating) conjunction, but not beginning with a subordinating conjunction:

• But his plan failed. [OK]
• Because his plan failed. [Wrong - fragment]

Of course, this is a simplistic approach. And descriptive grammars such as The Cambridge Grammar of the English Language have shown that the FANBOYS are far from a homogenous grouping. But many teachers feel that they are useful mnemonic for younger learners.

As to your question, you ask:

What is so special about the FANBOYS conjunctions that they are said to stand outside of independent clauses, while the rest are said to be part of otherwise-independent clauses, making them subordinate?

You are certainly right to point out the explanatory circularity and that removing both coordinating and subordinating conjunctions results in correct, free-standing clauses. His plan failed in the case above. Nevertheless, there is one essential difference between the two types.

Clauses beginning with a subordinating conjunction (i.e. dependent clauses) can be placed before or after the independent clause:

• His plan failed because he had overlooked an important detail.
• Because he had overlooked an important detail, his plan failed.

On the other hand, clauses beginning with a coordinating conjunction (i.e. independent clauses) must follow the previous independent clause:

He had overlooked an important detail, so his plan failed.

*So his plan failed, he had overlooked an important detail is ungrammatical.

Extrapolating to your examples, you can say both:

• Stock prices would have plummeted, unless the company had issued a public apology.
• Unless the company had issued a public apology, stock prices would have plummeted.

But only:

Stock prices would have plummeted, but the company issued a public apology.

and not:

*But the company issued a public apology, stock prices would have plummeted.

Answer 2

I have also wondered what exactly makes one subordinating vs. coordinating.
BUT keep in mind that 'ing' at the end of "subordinating". The conjunction itself subordinates or coordinates a clause. It is not something about the nature of each clause, but what the conjunction does to the clause.

"Stock prices plummeted and the company issued an apology."
"Stock prices plummeted although the company issued an apology."
Even though this particular "and" would sound odd if you reversed the order, because there is an implied time sequence, still, if one clause is more essential than the other, it is not because the conjunction tells us so. In the case of 'because', 'although', 'if', 'when', 'where', and I'd say 'unless', on the other hand, that one word tells us that one clause is the point and the other is a detail or a condition. That's NOT because one of the facts mentioned is inherently less important, but because the conjunction makes it less important.

"I slept well because I had just worked for 16 hours trying to separate a pair of conjoined twins."

Obviously, the main clause "I slept well" is far less interesting, but that conjunction alone makes the other part "subordinate".

Answer 3

Your example sentence with the "unless" doesn't make any sense.

The sentence should be written as follows:

"Stock prices would have plummeted if the company hadn't issued a public apology."

Note that there's no need for a comma between the two clauses as the sentence begins with an independent clause.

This construction has a different meaning than the sentence you wrote with "but" as a coordinator, which you implied had the same meaning as the poorly constructed one.

The subordinate clause beginning with "if" acts as an adverb telling under what conditions the stock prices would have plummeted. In other words, that clause modifies the verb in the independent clause, ensuring its role as subordinate to it.

Answer 4

In some linguists' accounts, coordinate conjunctions conjoin constituents of the same category, where the category of a constituent includes information about any item which has been moved away (such as a question word). Other connecting words are not limited in this way to connecting constituents of the same category.

The acceptability of (1-3) is evidence that "and", "but", "unless" are all coordinating:

 (1) What did [Jack like __]  and [Louise reject ___]?  
 (2) What did [Jack like __]  but [Louise reject ___]?  
?(3) What did [Jack like __]  unless [Louise would reject ___]?

Except, I'm not sure about the acceptability of (3). If it is actually ungrammatical, that suggests that "unless" is not coordinating.

(Perhaps some of you can come up with clearer examples.)

The above is derived from McCawley's extensive discussion of coordination in Chapter Nine of his The Syntactic Phenomena of English, some of which is available on line: McCawley on coordination, see p. 267-.