Editing Conjunction (grammar) (section)

==Separation of clauses==
Commas are often used to separate [[clause]]s. In English, a comma is used to separate a [[dependent clause]] from the [[independent clause]] if the dependent clause comes first: ''After I fed the cat, I brushed my clothes.'' (Compare this with ''I brushed my clothes after I fed the cat.'') A [[relative clause]] takes commas if it is non-[[restrictiveness|restrictive]], as in ''I cut down all the trees, which were over six feet tall.'' (Without the comma, this would mean that only the trees more than six feet tall were cut down.) Some style guides prescribe that two [[independent clause]]s joined by a coordinating conjunction (''for'', ''and'', ''nor'', ''but'', ''or'', ''yet'', ''so'') must be separated by a comma placed before the conjunction.<ref name=Fowler3rev1>{{Cite book | author1=Fowler, H. W. | author2-link=Robert Burchfield | author2=Burchfield, R. W. | title=The New Fowler's Modern English Usage | edition=Third, revised | year=2000 | publisher=Oxford University Press | location=Oxford | isbn=0-19-860263-4 | page=[https://archive.org/details/newfowlersmodern0000fowl_2000/page/162 162] | author1-link=Henry Watson Fowler | url=https://archive.org/details/newfowlersmodern0000fowl_2000/page/162 }}</ref><ref name="getitwriteonline1">{{cite web|author=Nancy Tuten |url=https://getitwriteonline.com/articles/when-to-use-comma-before-and/ |title=When to Use a Comma before "And" |work=Getitwriteonline.com |access-date=2012-03-25}}</ref> In the following sentences, where the second clause is independent (because it can stand alone as a sentence), the comma is considered by those guides to be necessary:
* ''Mary walked to the party, but she was unable to walk home.''
* ''Designer clothes are silly, and I can't afford them anyway.''
* ''Don't push that button, or twelve tons of high explosives will go off right under our feet!''
In the following sentences, where the second half of the sentence is not an independent clause (because it does not contain an explicit [[subject (grammar)|subject]]), those guides prescribe that the comma be omitted:
* ''Mary walked to the party but was unable to walk home.''
* ''I think designer clothes are silly and can't afford them anyway.''
However, such guides permit the comma to be omitted if the second independent clause is very short, typically when the second independent clause is an [[imperative mood|imperative]],<ref name="Fowler3rev1"/><ref name="getitwriteonline1"/> as in:
* ''Sit down and shut up.''
The above guidance is not universally accepted or applied. Long [[coordinate clause]]s are nonetheless usually separated by commas:<ref>{{cite book|last=Swan |first=Michael |year=2006 |title=Practical English Usage |publisher=Oxford University Press}}</ref><!-- This was inserted as though it contradicts the above rules, but it does not. "She would never have dreamed of taking what was not hers," is an independent clause, which would already be separated by a comma according to the guidance discussed above. Perhaps the example could be moved under the rule about independent clauses, and the main text should say "independent clauses, which can include long coordinate clauses". -->
* ''She had very little to live on, but she would never have dreamed of taking what was not hers.''

A comma between clauses may change the connotation, reducing or eliminating [[ambiguity]]. In the following examples, the thing in the first sentence that is very relaxing is the cool day, whereas in the second sentence it is the walk, since the introduction of commas makes "on a cool day" parenthetical:

:''They took a walk on a cool day that was very relaxing.''

:''They took a walk, on a cool day, that was very relaxing.''

If another prepositional phrase is introduced, ambiguity increases, but when commas separate each clause and phrase, the restrictive clause can remain a modifier of ''the walk'':

:''They took a walk in the park on a cool day that was very relaxing.''

:''They took a walk, in the park, on a cool day, that was very relaxing.''

In some languages, such as [[German language|German]] and [[Polish language|Polish]], stricter rules apply on comma use between clauses, with dependent clauses always being set off with commas, and commas being generally proscribed before certain coordinating conjunctions.

The joining of two independent sentences with a comma and no conjunction (as in ''"It is nearly half past five, we cannot reach town before dark."'') is known as a ''[[comma splice]]'' and is sometimes considered an error in English;<ref>{{cite book |last=Strunk |first=William |date=May 2007 |title=The Elements of Style |publisher=Filiquarian Publishing |isbn=978-1-59986-933-9 |page=12 |quote=Do not join independent clauses by a comma.}}</ref> in most cases a semicolon should be used instead. A comma splice should not be confused, though, with the literary device called ''[[asyndeton]]'', in which coordinating conjunctions are purposely omitted for a specific stylistic effect.