Conjunctions connect words, phrases, or clauses and at the same time indicate the relationship between them. Conjunctions include the simple coordinating conjunctions (and, but, or, for, nor, so, yet), the subordinate conjunctions (because, since, although, when, if, so that, etc.), the correlative conjunctions (either ...or, neither ... nor, both ... and), and the conjunctive adverbs (however, thus, furthermore, etc.).
The simple coordinating conjunctions are and, but, or, for, nor, so, and yet. They often connect two independent clauses (complete thoughts):
- The program designer established the default settings, and the programmer built them into the system.
- Our proposal was a day late, but we were not eliminated from competition.
- The pump will have to be replaced, or we will continue to suffer daily breakdowns.
- We rejected his budget, yet he continued to argue that all contested items were justified.
These simple connectors establish the relationship between the thoughts being coordinated:
- —And shows addition
- —Or shows alternative
- —Nor shows negative alternative
- —But and yet show contrast
- —For and so show causality
NOTE 1: When you use a coordinating conjunction to connect two independent clauses or complete thoughts, place a comma before the conjunction, as in the sentences above. However, you may omit the comma when the two clauses are short and closely related. Also, a semicolon can replace both the comma and the conjunction. See SEMICOLONS and COMMAS.
NOTE 2: The conjunctions and and or (preceded by a comma) also connect the last two items in a series:
- The engineer designed an emergency exit door, a narrow outside stairway, and a concrete support pad.
- She requested full written disclosure, an apology, or financial compensation.
Ensure that in choosing and and or you select the conjunction that conveys exactly what you mean.
At first glance, and and or merely join two or more items, but they can and often do imply much more.
In the following sentences and does more than merely connect the ideas. What and implies is stated in parentheses following each example:
- He saw the accident, and he called the police. (therefore)
- My boss is competent, and David is not. (contrast)
- He changed the tire, and he replaced the hub cap. (then)
- Explain the cost savings, and I’ll approve your proposal. (condition)
The conjunction or usually means one of two possibilities:
- I want either a Ford or an Acura.
However, or sometimes has other, occasionally confusing, implications:
- The faulty part or the worm gear seemed to be causing our problem. (Are the faulty part and the worm gear the same? Only knowledgeable readers would know for sure.)
- Add to the bid, or I’ll reject your offer. (negative condition)
- He began doing the schematics, or at least he appeared to be doing them. (correction)
See AND/OR in WORD PROBLEMS.
Occasionally, sentences can begin with a coordinating conjunction.
This advice contradicts the rule that many of us learned in school: “Never begin a sentence with and.” Some writers and editors still offer this advice, but most have now recognized that this so-called rule has no basis. Even Shakespeare began some of his sentences with coordinating conjunctions.
A coordinating conjunction at the beginning of a sentence links the sentence to the preceding sentence or paragraph. Sometimes, the linking is unnecessary:
- We objected to the proposal because of its length. And others felt that it had errors in its facts.
The and at the beginning of the second sentence is simply unnecessary. It adds nothing to the thought and may easily be omitted:
- We objected to the proposal because of its length. Others felt that it had errors in facts.
Using a conjunction to begin a sentence is not grammatically incorrect. Sometimes, it is good stylistic variation. But it tends to look and sound informal, so avoid this practice in formal documents.
Do not use and or but before which (or that, who, whose, whom, where) unless you use a preceding parallel which (or that, who, whose, whom, where):
- We explored the DeMarcus itinerary, which you explained in your letter but which you failed to mention in Saturday’s meeting.
- The meetings should take place where we met last year or where we can arrange for equally good facilities.
The following sentence violates this principle. Consequently, it is awkward and nonparallel:
- The plans called for a number of innovative features, especially regarding extra insulation, and which should save us much in fuel costs. (Deleting the and would solve the lack of parallelism in this sentence.)
In contrast to the limited set of coordinating conjunctions, subordinate conjunctions are a varied and diverse group:
- after, although, as, because, before, if, once, since, that, though, until, when, where, while
- in that, so that, such that, except that, in order that, now (that), provided (that), supposing (that), considering (that), as far as, as long as, so long as, sooner than, rather than, as if, as though, in case
- if . . . (then)
- although . . . yet/nevertheless
- as . . . so
- more/–er/less . . . than
- as . . . as
- so . . . (that)
- such . . . as
- such . . . (that)
- no sooner . . . than
- whether . . . or (not)
- the . . . the
Subordinate conjunctions introduce subordinate clauses and phrases (dependent clauses and phrases that do not convey complete thoughts and are therefore not independent):
- After the engineer gave her talk
- Because of the voltage loss
- When the test results come in
- While still producing fluids
- In that you had already made the request
- Except that the procedure was costly
- Provided that you calculate the results
- As though it hadn’t rained enough
- If we fail
- As aware as he is
- So expensive that it was prohibitive
- Whether or not you submit the report
These subordinate clauses and phrases must be attached to independent clauses (complete thoughts) to form sentences:
- After the engineer gave her talk, several colleagues had questions.
- In that you had already made the request, we decided to omit the formal interview.
- If we fail, the project stops. (or If we fail, then the project stops.)
- As aware as he is, he must be sensitive to the personnel problems.
NOTE 1: A subordinate clause or phrase that opens a sentence should be followed by a comma. The preceding sentences illustrate this rule. See COMMAS.
NOTE 2: When the subordinate clause or phrase follows the independent clause or main thought of the sentence, no commas are necessary:
- The experiment failed because of the voltage loss.
- We would have denied the request except that the procedure was so costly.
- We wondered whether you would turn in your report.
NOTE 3: Occasionally, the subordinate clause or phrase interrupts the main clause and must have commas on both sides of it to indicate where the clause or phrase appears:
- The President and the Joint Chiefs of Staff, after receiving the latest aerial reconnaissance photos of the area, decided on a naval blockade of all ports.
- Our budgetary problems, regardless of the Madiera Project expense, would have taken care of themselves if the prime rate hadn’t gone up three points.
Subordinate conjunctions can begin sentences:
- When the test results come in, we’ll have to analyze them carefully.
- Because the project manager was unfamiliar with the budget codes, we failed to expense the costs of fabrication.
NOTE: The old-school rule “Never begin a sentence with because” was and remains a bad rule. You may begin a sentence with because as long as the dependent clause it introduces is followed by an independent clause or complete thought.
Distinguish between some subordinate conjunctions that have overlapping or multiple meanings (especially because/since/as and while/although/as).
Avoid using since and as to mean “because”:
- Because the Leiper Project failed, several engineers were reassigned to electro-optics. (not Since the project failed . . . )
- Because we had ample supplies, no new batteries were ordered. (not As we had ample supplies . . . )
Avoid using while and as to mean “although”:
- Although many employees begin work at 8 a.m., others begin at 7 a.m. (not While many employees begin work at 8 a.m.... )
- Although the value of the test results declined, we still felt we could meet the deadline. (not As the value of the test results declined . . . )
Correlative conjunctions are pairs of coordinating conjunctions:
- both . . . and
- either . . . or
- neither . . . nor
- not only . . . but also
Make the constructions following each coordinating conjunction parallel:
- The committee was interested in both real estate holdings and stock investments. (not . . . both in real estate holdings and the stock investments.)
- The investigation revealed that either the budget was inaccurate or our records had gaps. (not The investigation revealed either that the budget was inaccurate or our records had gaps.)
NOTE: Faulty parallelism problems occur when the same phrase structure or word patterns do not occur after each coordinating conjunction:
- He was aware that not only was the pipe too small but also that the pipe supports were made of aluminum instead of stainless steel.
This sentence is confusing because the two thats are not parallel. The first that comes before not only, and the second that comes after but also. A parallel version of the sentence is much smoother:
- He was aware not only that the pipe was too small but also that the pipe supports were made of aluminum instead of stainless steel.
Conjunctive adverbs are adverbs that function as conjunctions, typically by connecting independent clauses or complete thoughts. Usually, a semicolon appears along with the conjunctive adverb. The most common conjunctive adverbs are accordingly, also, besides, consequently, further, furthermore, hence, however, moreover, nevertheless, otherwise, then, therefore, thus, and too. See TRANSITIONS.
NOTE: Conjunctive adverbs and the accompanying semicolons lengthen sentences and convey a heavy, formal tone. If possible, replace conjunctive adverbs with and, but, or, for, nor, so, and yet.
Use a semicolon before and a comma after conjunctive adverbs used to join two complete thoughts:
- Motherboard assembly is a lengthy production process; however, the individual assembly steps must still be tightly controlled.
- Increasing pressure in the T-valves is potentially dangerous; nevertheless, we will not be able to monitor effluent discharge without increasing the pressure.
See SEMICOLONS and COMMAS.
NOTE: You can omit the comma following the conjunctive adverb if the sentence is short:
- I think; therefore I am.
Use a comma following conjunctive adverbs at the beginning of a sentence:
- Therefore, I am recommending that Pharmaco reconsider the baseline scores for the principal efficacy parameters.
- However, sulfur compounds might not be the answer either.
NOTE 1: You may omit this comma if the sentence is short:
- Thus the plan failed.
NOTE 2: If the adverb appears at the beginning of the sentence but does not behave as a conjunction, it is part of the sentence and cannot be followed by a comma:
- Then the seam split at the forward discharge valve, and the boiler lost pressure rapidly.
- Regardless of how we examined the problem, we could not resolve the fundamental dispute between the software designers and the copyright holders.