A conjunction is a grammatical element that connects linguistic units such as words, phrases, clauses, or whole sentences. Conjunctions perform the simple but essential task of showing relationships—coordination, subordination, choice, contrast, cause, and time—between the connected elements. In most languages conjunctions are a closed class of short, frequent words: for example in English, common conjunctions include and, but, or, because, although, if, and until.

Major types

  • Coordinating conjunctions join elements of equal grammatical status (words with words, phrases with phrases, independent clauses with independent clauses). English coordinating conjunctions are often remembered by the acronym FANBOYS: for, and, nor, but, or, yet, so.
  • Subordinating conjunctions introduce dependent (subordinate) clauses and show relationships such as cause, time, condition, or concession. Examples: because, although, if, when, while, since, unless.
  • Correlative conjunctions work in pairs to link balanced structures: either...or, neither...nor, both...and, not only...but also, whether...or.

Functions and punctuation

Conjunctions indicate how the linked elements relate: addition (and), contrast (but), choice (or), result (so), reason (because), time (when). Punctuation rules depend on the clause structure. When a coordinating conjunction joins two independent clauses, a comma before the conjunction is standard in formal writing: "She was tired, but she kept working." When a subordinating conjunction begins a dependent clause that precedes the main clause, a comma usually follows the dependent clause: "Because it rained, we stayed home." If the main clause comes first, the comma is typically omitted: "We stayed home because it rained."

Examples and usage notes

  • Words: "bread and butter"
  • Phrases: "in time and on budget"
  • Clauses: "I called, but he did not answer."
  • Correlative pairing: "Not only did she finish, but she improved the design."

Writers sometimes begin sentences with coordinating conjunctions such as "But" or "And." This practice has a long history in English prose and is widely accepted in modern usage for emphasis, contrast, or stylistic rhythm, though it may be avoided in very formal contexts. Another class, conjunctive adverbs (however, therefore, moreover), behave like connectors but are grammatically distinct and often require semicolons or commas.

History and cross-linguistic perspective

The term "conjunction" comes from Latin roots meaning "joining together" and has been part of traditional grammar descriptions since antiquity. Languages differ in how they mark subordination and coordination: some use particles or affixes rather than separate words, while others rely on word order. Understanding conjunctions is fundamental for analyzing sentence structure, expressing complex ideas, and achieving clarity in both spoken and written communication.

Notable distinctions include the difference between conjunctions and prepositions (conjunctions link clauses; prepositions relate nouns or pronouns to other words) and the careful use of correlative pairs to maintain parallel sentence structure. Mastering conjunctions improves coherence and rhetorical effect across registers and genres.