If you read me really, really closely (I put those double adverbs in there just for you!),

At some point in our lives, early on, maybe in grade school, teachers give us a pat definition for a sentence—“It begins with a capital letter, ends with a period and expresses a complete thought.” We eventually learn that that period might be replaced by another strong stop, like a question mark or an exclamation point.

 

But that definition misses the essence of sentencehood. We are taught about the sentence from the outside in, about the punctuation first, rather than the essential components. The outline of our boat, the meaning of our every utterance, is given form by nouns and verbs. Nouns give us sentence subjects—our boat hulls. Verbs give us predicates—the forward momentum, the twists and turns, the abrupt stops.

 

For a sentence to be a sentence we need a What (the subject) and a So What (the predicate). The subject is the person, place, thing or idea we want to express something about; the predicate expresses the action, condition or effect of that subject. Think of the predicate as a predicament—the situation the subject is in.

 

I like to think of the whole sentence as a mini-narrative. It features a protagonist (the subject) and some sort of drama (the predicate): The searchlight sweeps. Harvey keeps on keeping on. The drama makes us pay attention.

 

Let’s look at some opening lines of great novels to see how the sentence drama plays out. Notice the subject, in bold, in each of the following sentences. It might be a simple noun or pronoun, a noun modified by an adjective or two or something even more complicated:

 

“They shoot the white girl first.” —Toni Morrison, “Paradise”

 

“Stately, plump Buck Mulligan came from the stairhead, bearing a bowl of lather on which a mirror and a razor lay crossed.” —James Joyce, “Ulysses”

 

“The Miss Lonelyhearts of the New York Post-Dispatch (Are-you-in-trouble?—Do-you-need-advice?—Write-to-Miss-Lonelyhearts-and-she-will-help-you) sat at his desk and stared at a piece of white cardboard.” —Nathanael West, “Miss Lonelyhearts”

 

Switching to the predicate, remember that it is everything that is not the subject. In addition to the verb, it can contain direct objects, indirect objects, adverbs and various kinds of phrases. More important, the predicate names the predicament of the subject.

 

“Elmer Gantry was drunk.” —Sinclair Lewis, “Elmer Gantry”

 

“Every summer Lin Kong returned to Goose Village to divorce his wife, Shuyu.” —Ha Jin, “Waiting”

 

There are variations, of course. Sometimes the subject is implied rather than stated, especially when the writer uses the imperative mood:

 

“Call me Ishmael.” —Herman Melville, “Moby-Dick”

 

And sometimes there is more than one subject-predicate pairing within a sentence:

 

“We started dying before the snow, and like the snow, we continued to fall.” —Louise Erdrich, “Tracks”

 

One way to get the hang of such mini-narratives is to gently imitate great one-liners. Try taking each one of the sentences above and plugging in your own subjects and predicates, just to sense the way that nouns and verbs form little stories.

 

Another way to experiment with subjects and predicates is to write your epitaph — either seriously or in jest. The editors of Smith Magazine challenged their readers to put their lives into six words and have published the best results. Here are two  Six-Word Memoirs that do the subject-predicate tango:

 

“Told to Marry Rich, married Richard.” (JMorris)

 

“My parents should’ve kept their receipt.” (SarahBeth)

 

When a sentence lacks one of its two essential parts, it is called a sentence fragment. Like the flotsam I mentioned earlier, fragments are adrift, without clear direction or purpose.

 

Playing with sentence fragments can be fun — the best copywriters use them for memorable advertising slogans (Alka-Seltzer’s “Plop plop, fizz fizz”). But there are plenty of competing Madison Avenue slogans to convince you that a full sentence registers equally well—from Esso’s “Put a tiger in your tank” to the Heublein Company’s “Pardon me, would you have any Grey Poupon?” While sentence fragments can be witty, they are still shards of thoughts, better suited to hawking antacids than to penning the Great American Novel or earnestly attempting to put inchoate thoughts into indelible words.

 

If sentence fragments are like flotsam, a profusion of subjects is like jetsam. Too many subjects thrown in can cause a passage to become muddy. We are especially prone to losing control of our subjects when we speak. Take these off-the-cuff remarks by President George H. W. Bush at a 1988 Milwaukee campaign stop around Halloween:

 

“We had last night, last night we had a couple of our grandchildren with us in Kansas City—6-year-old twins, one of them went as a package of Juicy Fruit, arms sticking out of the pack, the other was Dracula. A big rally there. And Dracula’s wig fell off in the middle of my speech and I got to thinking, watching those kids, and I said if I could look back and I had been president for four years: What would you like to do? Those young kids here. And I’d love to be able to say that working with our allies, working with the Soviets, I’d found a way to ban chemical and biological weapons from the face of the earth.”

 

As the subjects in those sentences keep shifting—from we to twins, one of them, the other, we (implied), wig, I, I, I, you, kids, I, and I—his message keeps shifting, too. Mr. Bush’s speechwriter, Peggy Noonan, has written that the president was “allergic to I.” He seemed to feel uncomfortable calling attention to himself, so he performed what Noonan called “I-ectomies” in his speeches.

 

Vice President Joseph R. Biden Jr. may not share Mr. Bush’s aversion to I, but a sentence from his 2008 vice-presidential debate shows how he, too, could lose track of his subjects:

 

“If you need any more proof positive of how bad the economic theories have been, this excessive deregulation, the failure to oversee what was going on, letting Wall Street run wild, I don’t think you needed any more evidence than what you see now.”

 

Biden not only shifts from you to I and back to you again, he throws three sentence fragments into the middle of his sentence, each featuring a different subject.

 

Syntax gets a lot more complicated than subjects and predicates, but understanding the relationship between the hull and the sail, the What and the So What, is the first step in mastering the dynamics of a sentence.

 

Just as there is no one perfect boat, there is no one perfect sentence structure. Mark Twain wrote sentences that were as humble, sturdy and American as a canoe; William Faulkner wrote sentences as gaudy as a Mississippi riverboat. But no matter the atmospherics, the best sentences bolt a clear subject to a dramatic predicate, making a mini-narrative.

 

-—Constance Hale

 

{A version of this article appears in Draft, a series about the art and craft of writing in the Opinionator section of the New York Times.}