Common sentence construction problems

Sentence construction describes how a sentence’s different parts are put together, from its punctuation to the ordering of its words.

This article looks at some of the most common types of sentence construction problems to help you avoid them in your own writing. These include both grammatical errors and problems with clarity.

Sentence construction problems take a nearly infinite number of forms, and at times sentences are so poorly constructed that identifying the problems is almost impossible. By contrast, ideally clear sentences are relatively rare. In fact, clear sentences are written as much by avoiding what’s bad as by pursuing what’s good.

Run-on sentences

A run-on sentence emerges when phrases that could stand alone as individual sentences are joined together without the proper punctuation (put in technical terms, a run-on sentence occurs when two or more “independent clauses” are joined together without proper punctuation).

Notice that the definition of run-on sentence has to do with grammar, not style—people sometimes call very long and unwieldy sentences “run-on sentences,” but this is an abuse of the term, and run-on sentences can be fairly short.

They come in many varieties, but here are a few of the most common run-on sentences:

Comma splice

Simply put, a comma splice is a comma placed where a period would normally go, without a coordinating conjunction to follow (the coordinating conjunctions are as follows: for, and, nor, but, or, yet, so).

The more technical (and precise) definition of comma splice is as follows: two independent clauses separated by a comma without a coordinating conjunction following the comma.

Examples: Comma splice

Home brewing beer and wine kits have appeared in more households than ever over the past ten years, people have never before rushed with such vigour to sacrifice the quality of the drinks for the pleasure of hands-on brewing.

Home brewing beer and wine kits have appeared in more households than ever over the past ten years, and people have never before rushed with such vigour to sacrifice the quality of the drinks for the pleasure of hands-on brewing.

Home brewing beer and wine kits have appeared in more households than ever over the past ten years. People have never before rushed with such vigour to sacrifice the quality of the drinks for the pleasure of hands-on brewing.

The error is not arbitrary, and the comma splice can cause much confusion in even slightly more complicated sentences. In the following sentence, for instance, the comma splice creates confusion because we don’t know to which part of the sentence “when he drank it warm” should attach.

Does he like cream and sugar when he drink coffee warm, or does he like coffee black when he drinks it warm?

Examples: Confusing comma splice

Jimmy liked to take cream and sugar with his coffee, when he drank it warm, he would also like it black.

Jimmy liked to take cream and sugar with his coffee; when he drank it warm, he would also like it black.

Jimmy liked to take cream and sugar with his coffee, when he drank it warm; he would also like it black.

“And” or “but” without a comma

Simply put, this form of run-on sentence occurs when “and” or “but” (or another coordinating conjunction) is placed where a period would normally go, without being preceded by a comma.

The more technical (and precise) definition of this error is as follows: two independent clauses separated by a coordinating conjunction (any of these: for, and, nor, but, or, yet, so) without being immediately preceded by a comma.

Notice the similarity between this error and the comma splice error. This error, similarly, is one that produces confusion. Because we use “and” and “but” (and the others) so often and for so many purposes, it’s useful to know how these words are being used when we encounter them.

Unless being used in a list, the comma + coordinating conjunction formula signals to the reader that she’s likely about to read a new, related, and complete thought. In other words, it helps us navigate sentences.

Examples: Confusing “and” without a comma

Home brewing beer and wine kits have appeared in more households than ever over the past ten years and people have never before rushed with such vigour to sacrifice the quality of the drinks for the pleasure of hands-on brewing.

Home brewing beer and wine kits have appeared in more households than ever over the past ten years, and people have never before rushed with such vigour to sacrifice the quality of the drinks for the pleasure of hands-on brewing.

Home brewing beer and wine kits have appeared in more households than ever over the past ten years. People have never before rushed with such vigour to sacrifice the quality of the drinks for the pleasure of hands-on brewing.

Sentence fragments

A sentence fragment emerges any time something that couldn’t stand alone as a sentence appears alone as a sentence or fails to connect properly to the sentence it’s in. In other words, every sentence fragment involves a phrase that should have what it takes to be a sentence but doesn’t.

Remember, for a string of words to be considered a sentence, we have to have a “subject” and “predicate.” A subject is what does an action, while the predicate is the act. Put another way, the subject is the “nouny” part of a sentence, while the predicate is the “verby” part.

Some sentences have more than one subject-predicate combination, but the sentence always begins with in the subject position.

See below for examples of subjects and predicates in different kinds of sentences, with different kinds of punctuation. Remember, no matter how many subjects-predicate pairs come in a sentence, the ratio is always 1:1—every acceptable subject has a predicate; every acceptable predicate has a subject.

Examples: Sentences divided by subject and predicate

Ducks / fly.

Haggard and elderly ducks and geese / fly slower, lower, and with more caution.

Haggard and elderly ducks and geese / fly slower, lower, and with more caution, perhaps because of rheumatism.

Haggard and elderly ducks and geese / fly slower, lower, and with more caution, perhaps because their rheumatism / hinders them.

Ducks / fly; dogs / walk.

Ducks / fly faster than geese when dogs / run and bark.

The dog / catches the ball.

The dog / catches the ball, which / is covered in slobber.

The dog / catches the ball, which we / bought.

The ball / is caught.

The ball / now has the following characteristics: a slipperiness, a smelliness, and a chewiness.

The ball / now has the following characteristics: it / is slippery, it / is smelly, and it / is chewy.

The ball / now has the following characteristics: it / is slippery, smelly, and chewy.

Some common forms of sentence fragment involve breaking a sentence up with confused punctuation, while others arise from incomplete sentences being punctuated as if they were full sentences.

(note: Sentence fragments are sometimes used stylistically in journalism and creative writing, often as nouns or noun phrases standing alone, beginning with a capital and ending with a period. Appropriate use of sentence fragments in academic or formal writing is very rare.)

Semicolon for a comma

In the below example, the rules of semicolon use mean that the phrase that comes after the semicolon in the sentence below should have a subject and a predicate (i.e. it should be able to stand alone as a sentence).

“A noble pursuit,” though, is a lone subject, and there is no verb, so no predicate to accompany the subject. This makes it a sentence fragment.

Examples: Semicolon for a comma

The best way to ensure a happy life / is to study philosophy; a noble pursuit.

The best way to ensure a happy life / is to study philosophy, a noble pursuit.

Semicolon for a colon

A similar problem looms here, with only a subject (in this case, a bunch of nouns) following the semicolon.

Examples: Semicolon for a colon

He / would take only three things on his journey; his clothes, his bed roll, and his trusty walking stick.

He / would take only three things on his journey: his clothes, his bed roll, and his trusty walking stick.

Colon misused after verb

The problem here is a bit different. Here, the predicate is present, but it’s incomplete because the colon is misused. More specifically, the colon can’t be used immediately after “indicated” since “indicated,” as used here, requires something to follow (we still need to know what the study indicated).

Examples: Misused colon

The results of the study / indicated: three of the men, three of the children, and three of the women / were related.

The results of the study / indicated that three of the men, three of the children, and three of the women / were related.

The results of the study / indicated the following: three of the men, three of the children, and three of the women / were related.

“–ing” form of a verb misused

Sometimes people use the “–ing” form (technically called the “present participle” form) of a verb as if it were the simple form. The difference here is that “–ing” verbs can’t do the grammatical work of simple verbs, which is to mark the beginning of the predicate.

The most common verb abused with this mistake is “to be,” which is conjugated as “being” when it should be conjugated “is” or “was.”

Examples: Misused “-ing” form of a verb

He / argued all night long. The point being important.

He / talked all night long. The point / was important.

He / talked all night long, the point being important.

No main verb (predicate) in the sentence

Although creative writers and journalists sometimes use noun phrases to form a string of words with a period at the end, we should recognize that these are not sentences, since they are usually composed of subjects without accompanying predicates.

In other words, a noun phrase alone can’t rise to the status of a sentence. Even if it begins with a capital and ends with a period, it’s not a sentence unless it has both a subject and predicate.

Examples: No main verb in the sentence

After they / settled the argument, they / became friends. A fortunate turn of events.

After they / settled the argument, they / became friends, a fortunate turn of events.

After they / settled the argument, they / became friends. It / was a fortunate turn of events.

After they / settled the argument, they / became friends. A fortunate turn of events it / was.

Subordinator leading the clause

Every good writer uses subordinators all of the time, and they include such familiar words as when, after, since, while, although, if, unless, because, while, and whereas. But a “subordinator” (also called a “subordinating conjunction”) transforms a phrase that can stand alone as sentence into a phrase that cannot (in technical terms, it transforms an “independent clause” into a “dependent clause”).

This transformation causes some writers grief. In these cases, unlike the ones above, we have a clear subject and predicate pair, but the subordinator requires the sentence to have a second subject-predicate pair in the sentence.

Examples: Subordinator leading the clause

They / would go to safety. When the coast / was clear.

They / would go to safety; when the coast / was clear.

They / would go to safety when the coast / was clear.

When the coast / was clear, they / would go to safety.

(note: see our article “Myth: It’s incorrect to start a sentence with ‘because’” for more examples and for information on subordinators and types of clauses)