English conjunctions fall into three families, each expressing a different relationship between the elements they join. Coordinating conjunctions (for, and, nor, but, or, yet, so) link grammatically equal elements; subordinating conjunctions (because, although, when, if) make one clause dependent on another; and correlative conjunctions (both...and, either...or, neither...nor, not only...but also) work in pairs to emphasize parallel relationships. Recognizing which type of conjunction is at work reveals the logical relationship the writer intends — addition, contrast, cause, condition, or choice.
Classify conjunctions encountered in reading by type and by the logical relationship they express. Then practice rewriting the same idea using all three conjunction types to see how each changes emphasis, clause status, and sentence structure.
You already know coordinating conjunctions (FANBOYS: for, and, nor, but, or, yet, so) and subordinating conjunctions (because, although, when, if, since, unless). This topic is about seeing those two families as part of a single three-part system — and adding the third member, correlative conjunctions — so you can make deliberate, informed choices about how to connect ideas.
The key distinction between the three families is what they do to the grammatical weight of the elements they join. Coordinating conjunctions treat both sides as equals: "I like coffee, and she likes tea" puts both clauses on the same footing. Neither depends on the other. Subordinating conjunctions, by contrast, create a hierarchy: one clause (the dependent one) is made to serve the other. In "I stayed in because it was raining," the because-clause explains the main clause — it has a supporting role, not an equal one. The choice between coordination and subordination is therefore a choice about logical emphasis: what do you want foregrounded?
Correlative conjunctions work in matched pairs: *both...and*, *either...or*, *neither...nor*, *not only...but also*. They share the coordinating conjunction's equality principle — both elements are still grammatically parallel — but they add rhetorical emphasis and scope. Compare "She is smart and hardworking" with "She is not only smart but also hardworking." The second version intensifies the claim and signals to the reader that both qualities are being asserted together as a unit. Because correlative conjunctions demand strict parallel structure between their two halves, they are both a stylistic tool and a grammatical constraint: "She is not only smart but also works hard" violates the parallelism rule (adjective vs. verb phrase).
The practical skill this framework gives you is rewriting for effect. Take any two related ideas and you can express their relationship in three ways: as equals with a coordinating conjunction, as a main-plus-support structure with a subordinating conjunction, or as a paired emphasis with a correlative conjunction. "He was tired, but he finished the report" (coordination, equal weight). "Although he was tired, he finished the report" (subordination — tiredness is a concession, finishing is the point). "Not only was he tired, but he also finished the report" (correlative — both facts are highlighted and the second is surprising). The ideas are the same; the structure tells the reader how to weigh them.