Sentence diagramming has tremendous value for students (and teachers!) of English grammar. Putting all of the words of a sentence on a diagram forces learners to identify the logical connections between different parts of the sentence. Students who diagram have to know how different parts speech work together to produce meaning; they can’t just memorize a few rules and label words without truly understanding their function.
But there’s an even more important benefit to diagramming: As the student moves on into high school, she can begin to use diagramming (as long as she’s studied it already) as a tool to fix weak sentences. Weak sentences usually stem from thinking problems—and diagramming can help the student locate those problem points.
A sentence which fits logically together is a sentence written in good style (poor style is most often the result of fuzzy thinking). Whenever a sentence doesn’t “sound right,”, the student should examine the logical relationships between the parts of the sentence. Diagramming the sentence lays the logic of the sentence bare and reveals any problems.
Consider the following balanced and beautiful sentence, from nineteenth-century poet Gerard Manley Hopkins:
Our prayer and God’s grace are like two buckets in a well; while the one ascends, the other descends.
Compare the sound of this sentence to a typical freshman composition thesis statement (this from an actual seminar paper I received several years ago from a student):
In Pride and Prejudice, her mother’s bad manners and wishing to get married made Elizabeth discontent.
While the second sentence makes sense, it’s an ugly sentence—the kind that makes parents and teachers despair.
If the middle-grade student is able to diagram both sentences, she’ll be able to see for herself why the first sentence resonates, while the second clunks.
In the Hopkins sentence, the subject and verb of the first independent clause are diagrammed like this:
The second sentence also has a compound subject and single verb:
But although the second sentence is grammatically correct, it’s ugly because the two subjects are two different kinds of words. “Manners” is a noun, while “wishing” is a gerund—a verb form used as a noun. Words which occupy parallel places on a diagram should take the same form—as in the Hopkins sentence, where “prayer” and “grace” are both nouns.
If the student sets out to fix the style problem in the second sentence, she’ll also be forced to clarify her thinking. The noun “manners” represents something that Elizabeth’s mother is doing to her; it’s an outside circumstance. The verb form “wishing” is internal; it’s Elizabeth’s own action which is forcing her to be discontent. The two causes of her discontent aren’t parallel. So what is the relationship between them? Do the mother’s bad manners represent an entire social sphere from which Elizabeth longs to escape? Does she wish for a more genteel life, and does she wish to get married because that will allow her to move from one kind of life to another? Or is marriage itself Elizabeth’s driving passion? Does she simply resent her mother’s bad manners because they jeopardize her chances of attracting a bridegroom?
The middle-grade student won’t yet be thinking on this level, but learning to diagram sentences will allow her to begin to understand the relationship between style and thought—and prepare her for more complex high school writing.
For a slightly different illustration of this, consider the following sentence, also drawn from a freshman composition assignment, and containing a very common sort of beginning-writer error: “In addition to the city, Theodore Dreiser’s society is depicted in its people.”
This is the kind of sentence that almost makes sense; it’s clear that the writer has an idea in mind, but that idea isn’t coming through to the reader. But how can the student locate the problem?
Through diagramming. In this case, the subject (society) and verb (is depicted) are diagrammed on a simple subject/verb line, with the prepositional phrase “in its people” diagrammed underneath the verb (it is acting as an adverb, because it answers the question “how”).
But where should “In addition to the city” go? It doesn’t seem to fit anywhere. Are the society and city both depicted? (If so, what’s the difference?) Is the society depicted in its people or in its city? (Neither is particularly clear.) The moral of this particular diagramming exercise: if you can’t put it on the diagram, it doesn’t belong in the sentence. The author of this sentence doesn’t exactly know what Dreiser is depicting, and he’s hoping to sneak his fuzzy comprehension past the reader.
One final example, this one slightly more subtle: “Therefore, the character of Irene is a summary of women of the time.” This is a very common sort of beginner sentence: it makes sense, but it sounds immature. Why?
The tip-off to the problem is the slanting line, which indicates that the noun to the right is a predicate nominative. A predicate nominative must rename the subject. But “summary” is not another word for “character.” The two are not even roughly parallel; a character can’t be a summary any more than an elephant can be a mouse.
To sum up: Diagramming isn’t an arcane assignment designed to torture the student. It forces students to clarify their thinking, fix their sentences, and put grammar to use in the service of writing—which is, after all, what grammar is for.