Considering Conditional Sentences

Including the different types and how to punctuate them correctly

Image by Roman Grac from pixabay.com

Similar to many other grammatical terms, “conditional sentences” doesn’t always ring a bell with writers — and a discussion of conditional sentences can get complicated.

Simply put, a conditional sentence tells what happens on the condition that something else happens. “If he passes the test, he’ll be accepted.” “They’ll arrive after they’ve crossed the bridge.” These are both conditional sentences.

The construction of conditional sentences

In my post “How to Correctly Create Connections with Conjunctions,” I explain that conjunctions connect words, phrases, and clauses in sentences. I also discuss the different types of conjunctions and list some of the most common conjunctions. Within the category of subordinate conjunctions, I list common examples, which include “after,” “if,” “since,” “unless,” “until,” and “when.”

I also use subordinate conjunctions in these sentences: “They ran home because it was late.” “They arrived early so they could set up.” “They decided they’d go whether they were invited or not.” In each of these sentences, the part that begins with a subordinate conjunction is secondary, or subordinate, to the main part and can’t stand alone.

The conditional clause within a conditional sentence is also a subordinate clause because it can’t stand alone. “If he passes the test” and “after they’ve crossed the bridge” from our two examples above don’t form complete sentences. Each is a clause, and each starts with a conjunction that introduces a condition. The remaining words in these sentences — “he’ll be accepted” and “they’ll arrive in town” — complete the message by providing details on what will happen when the condition presented by the clause introduced by a conjunction has been met.

Commas in conditional sentences

The general rule is to use a comma after a conditional clause but not before one. Consider this example again: “If he passes the test, he’ll be accepted.” In this conditional sentence the conditional clause “if he passes the test” begins the sentence, so a comma is needed at the end of the clause. Now consider this example again: “They’ll arrive in town after they’ve crossed the bridge.” In this conditional sentence the conditional clause “after they’ve crossed the bridge” ends the sentence, so a comma is not needed.

These two examples use two of the more common subordinate conjunctions used in conditional clauses, after and if. Here are a few more examples that show the general “add a comma after a conditional clause but not before one” rule:

Since he could reach the top shelf, he retrieved the bottle. He retrieved the bottle since he could reach the top shelf.

Unless they’re accompanied by an adult, children can’t attend. Children can’t attend unless they’re accompanied by an adult.

Until you’re 21, you can’t order a beer at a bar. You can’t order a beer at a bar until you’re 21.

When she opened the windows, the room cooled off. The room cooled off when she opened the windows.

Extra credit: Different types of conditional sentences

Conditional sentences can be broken into four categories: zero, first, second, and third. These are easy to remember as they relate to how likely a condition described in a conditional sentence is to occur. In a zero conditional sentence, it’s “extremely likely” that the condition mentioned will occur. Examples of zero conditional sentences include present-tense statements such as “If the dog goes outside while it’s raining, he gets wet” and “He gets hungry when he doesn’t eat.”

The next notch down in likelihood can be found in first conditional sentences, which describe something that’s “highly likely” to occur. An example is the warning “You’ll get stomach cramps if you swim too soon after eating.” You’ll notice that the result (“You’ll get stomach cramps”) is in future tense while the condition (“if you swim too soon after eating”) is in present tense. Only the conjunction if is used in first conditional sentences.

In second conditional sentences, the likelihood drops to “unlikely” as in “The basement would stay dry if the sump pump worked.” The conjunction if is used in these sentences, too, with the clause it creates in the simple past tense while the result of the condition is written with the word “would.”

A conditional sentence that describes a condition that can’t possibly be met is a third conditional sentence. Examples of this type of sentence include “He wouldn’t have gone to the party if he’d known his ex-girlfriend was going to be there.” Since this condition only existed in the past, it’s impossible to meet now. The use of “would have” with “if” indicates a third conditional sentence.

An earlier version of this post appeared in The Writing Cooperative.

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I write fiction, poetry, and nonfiction when I’m not working as a copy editor. Author of the novel *One Sister’s Song and the e-book [Not Nearly Everything You Need to Know About Writing](https://amzn.to/3mjSa2O). Learn more at my free [Writing Well](https://karendegrootcarter.substack.com/)* newsletter.