A CONJUCTION is used to link words, phrases, or clauses. Two types of conjunctions are coordinate conjunction (and, or, nor, but, etc.) and subordinate conjunctions (although, since, because, when, before, etc.)
Patterns to remember
Coordinate conjunctions may link similar ideas (and, not only… but also), opposite or contradictory ideas (but), or choices (either… or, neither…. nor). Pay attention to the meaning of the conjunction.
Incorrect: It is efficient or maintenance-free.
Correct: It is efficient and maintenance-free
Incorrect: We can take either a morning flight but an early afternoon flight.
Correct: We can take either a morning flight or an early afternoon flight.
Subordinate conjunctions show different kinds of relationships between two clauses. They may show cause and effect (because, so, as, since), time (when, while, after, before, until, as soon as), condition (if, unless), or a contradiction (even though, although). Again, pay attention to the meaning of the subordinate conjunction.
Incorrect: The machine shut off even though the power went off.
Correct: The machine shut off when the power went off.
Incorrect: I couldn’t call them until I don’t know their phone number.
Correct: I couldn’t call them because I don’t know their phone number.