How to Correctly Create Connections with Conjunctions

Including when a comma is — and isn’t — needed before one of these nifty little words

Image by David L from Pixabay

As a child of the 1970s, I learned about conjunctions from watching the three-minute, animated “Conjunction Junction” episode of Schoolhouse Rock! that popped up between full-length cartoons on Saturday mornings. When asked about the function of Conjunction Junction, a little railroad engineer hooking up train cars explained that Conjunction Junction connected words, phrases, and clauses, and his favorite train cars—labeled “and,” “but,” and “or”—helped him get most of his work done.

Types of conjunctions

Among the many things conjunctions can connect are independent clauses, which can stand on their own. Consider this compound sentence: “He went to the pharmacy, and she went to the hardware store.” Both “He went to the pharmacy” and “she went to the hardware store” could stand alone as individual sentences, so they’re independent clauses. In this example, though, they’re joined by the conjunction “and” to make a new sentence.

Conjunctions that connect two similar elements such as nouns, verbs, adjectives, adverbs, phrases, or independent clauses are called coordinating conjunctions because the two things they “coordinate” are similar. In addition to “and,” this group includes “but,” “for,” “nor,” “or,” “so,” and “yet.” A popular trick to remember this short list is to use the mnemonic FANBOYS: For And Nor But Or Yet So. Another example that shows a coordinating conjunction at work is “They bought a leash and a water bowl for their puppy.” In this example, “and” connects two nouns—“leash” and “water bowl.” In “They were tired yet happy,” “yet” connects two adjectives—“tired” and “happy.”

A correlative conjunction is always paired with another correlative conjunction to join elements that are similar. These pairings (“both/and,” “either/or,” “neither/nor,” “not only/but also,” “whether/or”) include a few words (“and,” “but,” “or”) that serve as coordinating conjunctions on their own. When those words appear in a sentence with their partners, though, they’re considered correlative conjunctions. Consider these examples: “They served both wine and beer.” “They decided to buy neither the big nor the small boat.”

“The car would get her not only to school but also to her job” provides another example of correlative conjunctions at work. I’d argue, though, that “also” could be deleted, changing this sentence to “The car would get her not only to school but to her job.” In the same way, “They went not only to show their support but also to speak with their cousin” could do without “also” as in “They went not only to show their support but to speak with their cousin.”

What’s more important is that the two things referenced in a sentence using correlative conjunctions are similar. In “The car would get her not only to school but also to her job,” for example, “school” and “her job” are both nouns. In “They went not only to show their support but also to speak with their cousin,” “show” and “speak” are verbs. Just as the elements connected by a coordinating conjunction need to match up, so do the elements connected by two correlative conjunctions.

Subordinating conjunctions, however, don’t connect two similar things. Instead, they connect an independent clause to a dependent, or subordinate, clause that they create. (For more on subordinate clauses, see my post “Subordinate Clauses Simplified.”) The full list of subordinating conjunctions is extensive, but the most common include “after,” “although,” “as,” “because,” “before,” “even if,” “even though,” “if,” “in case,” “once,” “only if,” “since,” “so” (which can serve as both a coordinating and a subordinating conjunction), “than,” “that,” “though,” “till,” “unless,” “until,” “when,” “whenever,” “where,” “wherever,” “whether,” and “while.”

Subordinating conjunctions work alone as in these sentences: “They ran home because it was late.” “They arrived early so they could set up.” “They decided to go whether they were invited or not.” You can see that the italicized subordinate clauses created by the subordinating conjunctions “because,” “so,” and “whether” are secondary to the main clauses in these sentences.

Using commas with conjunctions

Another important thing to understand is when a comma should — and should not — be added before a conjunction. The general rule is to add a comma before a coordinating conjunction (think FANBOYS: For And Nor But Or Yet So) when it connects two independent clauses as in our first example, “He went to the pharmacy, and she went to the hardware store.” If one of the two independent clauses joined by a coordinating conjunction is very short and there’s no chance of confusing readers, though, the comma can be left out. In “He woke early but she slept in,” for example, there’s no need for a comma before “but.”

In complex sentences (like those at the end of the discussion of subordinating conjunctions above), which have one independent clause and at least one dependent clause, a comma isn’t needed before the conjunction. In “They wanted to go to the party even though they weren’t invited,” for example, a comma shouldn’t be added before the conjunction “even though” since it begins a subordinate clause (a clause that can’t stand alone and is generally less important than the main clause).

In the case of the conjunction “so,” the use of a comma depends on how “so” is being used. In “The child jumped in the puddle so she could try out her new boots,” the word “so” is serving as a subordinating conjunction, so no comma is needed before it. In “The child was hungry, so her father cooked her some dinner,” the word “so” is a coordinating conjunction that connects two independent clauses (i.e., two equally important elements that can stand alone), so a comma should be added before it―just as a comma is used before “so” in this sentence and the one before it. For a nifty trick to help you remember this, see my earlier post, “When to Insert a Comma Before ‘So’.”

Key takeaways

• A coordinating conjunction connects two similar elements.

• Correlative conjunctions work in pairs to connect two grammatically parallel elements.

• A subordinating conjunction connects an independent clause to a dependent (subordinate) clause it creates.

• A comma is usually needed before a coordinating conjunction when it joins two independent clauses.

• No comma is needed before a subordinating conjunction that introduces a dependent clause.

• Use a comma when “so” joins two independent clauses; don’t use a comma when “so” introduces a dependent clause.

An earlier version of this post was published 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.