A "junction" is simply a place where things come together. The prefix "con" means "with," so a "conjunction" is, in one sense, a place where one thing joins with another. Grammatically, the term has become the name of a relatively small group of words that join clauses. Because we are interested in simplicity and in function, I want to include in this discussion the punctuation marks which serve the same purpose.

Using Coordinating Conjunctions

     "Ordinate" refers to rank, and "co" means "with," so "coordinating conjunctions join clauses that rank with each other, i.e., they are usually both main, and the ideas in them are approximately equal in level of importance. Perhaps the most common way of joining two such clauses is to use ", and" ", or" or ", but":

We went to the store, and we bought ice cream.
She went swimming, or maybe she went fishing.
I am old, but I am young at heart.

     Note that these conjunctions can be used to join two or more subordinate clauses: "She said [that he was late], and [that she no longer wanted to go]. The important point to remember is that they "CONjoin," i.e., join elements of equal grammatical value.

Using a Semicolon, Colon, or Dash

     Main clauses can also be joined by a colon, a semicolon, or a dash. Good writers use the semicolon to emphasize contrast:

The semicolon invites the reader to see and think about the differences between the two statements. As I tell my students, the semicolon brings us back to the level of Sesame Street's very important emphasis on "same and different." Note that the punctuation mark itself  (a period over a comma) can help you remember its function.

     The colon and dash are also used to communicate a logical relationship -- they make a distinction between the general and the specific. As in the preceding sentence, a general statement is made. The colon or dash indicates that what will follow will be a more detailed explanation of the same idea:

The difference between the colon and dash is entirely one of style and tone. The dash is generally considered to be casual, whereas the colon tends to be used in more formal writing.

The following words may function as subordinate conjunctions:

after, although, as, because, before, except, for, if, like*,  since, when, where, while, that, what, who, how, why, which, until, 'til, whenever, wherever, whatever, whoever, whichever, whether, but (when it means "except")

We can easily consider this "so" clause as an adverbial statement of result. But "So" at the beginning of a sentence functions as a coordinating conjunction for the simple reason that the period preceding it has signaled a dump to long-term memory, and thus the "main" clause to which it would be atached is no longer in STM:

    When it is used as a conjunction, you can consider "for" as either coordinating or subordinating. As with "so," the KISS approach is to consider it as coordinating when it is capitalized at the beginning of a sentence, and as subordinating when it is not capitalized and is preceded by ", "

For a theoretical discussion of "so" or "for," click on the words.

Punctuation, Meaning, and Style

     Consider the following two statements:

As they stand, they are two equally important, separate statements of fact. We could, if we wish, join them with ", and":

This, however, still leaves us with two equally important, separate statements of fact. Conceivably, we could join them with ", but":

The "but" changes the relationship by indicating a contrast between what he did, and what she did. A subtler, and perhaps stronger way of indicating this contrast is to use a semicolon:

Experienced readers will, I suggest, read the semicolon as an invitation to contemplate the differences expressed in the two main clauses. Whereas the ", but" tends to indicate a simple contrast of facts, the semicolon is more likely to lead readers to underlying implications: there is is again -- the men having fun while the women do the work.

     Whereas the ", and" ", but" and the semicolon conjoin the simple sentences as equals, we could use a subordinating conjunction to make one of the two statements relatively more important than the other. If he is the focus of the discussion, we might write:

On the other hand, if she is the focus, we would be more likely to write:

Punctuation is not simply a matter of etiquette -- it affects meaning. (For a related discussion, see MIMC.)

     As I suggest in the psycholinguistic model of how the brain processes language, good readers develop expectations about what is, or is not, probably coming in a sentence. A period, for example, unless it follows an abbreviated title (as in "Ms.") indicates to a reader that no more words should be coming that belong with the main clause that is currently in short-term memory. Thus the period signals the reader to dump the contents of STM to long-term memory thereby clearing STM for the next main clause. Subordinate conjunctions and punctuation marks affect a good reader's expectations.

Subordinate Conjunctions

     Once STM has been cleared, a good reader's brain is unconsciously, but decidedly looking for the subject of the next MAIN clause:

While he was sleeping, she watched TV.

She knew [he was sleeping].
That he was sleeping did not bother her.

Punctuation Marks

     Punctuation marks were developed to help readers quickly chunk appropriate groups of words into syntactic units. The developers of punctuation marks, whoever they were, did not consciously know about all this psycholinguistic stuff, but they did realize that, without some sort of standards for capitalization and punctuation, texts are extremely difficult to read. (Try it some time.) The rules of punctuation, therefore, were not meant simply to be "proper," as in rules of etiquette. They are guides to help the reader process the syntax of a sentence.
     As most of us learned in grade school, periods, question marks, and exclamation points are usually used to indicate the end of a main clause. There are a few exceptions to this, but they should become obvious as you do the exercises. A ", and" ", or" or ", but" indicate that something of the same grammatical type is coming, but the range of expectations is wide. It can range from a simple adjective (the old, but vigorous tree) to entire main clauses.

Dashes are less ambiguous. Although they are occasionally used to set off parenthetical expressions (which we refer to as "interjections") they generally indicate that what is coming is similar to what came before. Syntactically, however, that similarity can be expressed through a range of constructions -- from a main clause to, as in this sentence, a pair of prepositional phrases.

Colons, except when used in salutations of letters ("Dear Madame:"), usually indicate that what is coming are details or examples, thus, the same kind of idea as what preceded the colon.

Semicolons, as noted above, generally indicate that a contrasting idea is coming. Unlike dashes and colons, semicolons also signal the end of a main clause -- and thus a dump to long-term memory. This happens because semicolons have only two purposes (three, if you want to count their use in salutations). In addition to being used to end main clauses, they are used to separate items in a list, when individual items include commas (as in lists of addresses).  Because lists are obviously lists, and because salutations are obviously salutations, a semicolon in any other situation implies the end of a main clause.

* Like: Prescriptivists usually claim that "like" is a preposition, not a subordinate conjunction, and that "as" should be used instead of "like" to introduce subordinate clauses. But, as you will see, in spite of the prescriptivists, many people use "like" as a subordinate conjunction.
 

This border is a reproduction of

 Master Hare
1788, oil on canvas, Musée du Louvre, Paris
Carol Gerten's Fine Art http://metalab.unc.edu/cgfa/

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