When we coordinate things, whether we're talking about our schedules or our clothing, we make connections--or, as the dictionary says in a more fanciful way, "bring things together in a common and harmonious action." The same idea applies when we talk about coordination in grammar.
A common way to connect related words, phrases, and even entire clauses is to coordinate them--that is, connect them with a coordinating conjunction such as "and" or "but." The following short paragraph from Ernest Hemingway's Another Country contains several coordinated words, phrases, and clauses.
We were all at the hospital every afternoon, and there were different ways of walking across the town through the dusk to the hospital. Two of the ways were alongside canals, but they were long. Always, though, you crossed a bridge across a canal to enter the hospital. There was a choice of three bridges. On one of them a woman sold roasted chestnuts. It was warm, standing in front of her charcoal fire, and the chestnuts were warm afterward in your pocket. The hospital was very old and very beautiful, and you entered through a gate and walked across a courtyard and out a gate on the other side.
In most of his novels and short stories, Hemingway relies heavily (some readers might say too heavily) on such basic conjunctions as "and" and "but." The other coordinating conjunctions are yet, or, nor, for, and so.
Similar to these basic conjunctions are the following paired conjunctions (sometimes called correlative conjunctions):
both . . . andThe paired conjunctions serve to emphasize the words being connected.
either . . . or
neither . . . nor
not . . . but
not . . . nor
not only . . . but (also)
whether . . . or
Let's see how these correlative conjunctions work. First, consider the following simple sentence, which contains two nouns joined by and:
Merdine and Gus have gone to Buffalo.We can rewrite this sentence with paired conjunctions to emphasize the two nouns:
Both Merdine and Gus have gone to Buffalo.
We often use the basic coordinating conjunctions and paired conjunctions in our writing to connect related ideas.
Punctuation Tips: Using Commas with ConjunctionsWhen just two words or phrases are joined by a conjunction, no comma is needed:
Nurses in uniforms and in peasant costumes walked under the trees with the children.However, when two or more items are listed before a conjunction, those items should be separated by commas:
Nurses in uniforms, peasant costumes, and worn frocks walked under the trees with the children.
Similarly, when two complete sentences (called main clauses) are joined by a conjunction, we should generally place a comma before the conjunction:
The tides advance and retreat in their eternal rhythms, and the level of the sea itself is never at rest.Although no comma is needed before the and that joins the verbs advance and retreat, we do need to place a comma before the second and, which joins two main clauses.