AVOIDING COMMA SPLICES AND FUSED (RUN-ON) ERRORS IN COMPOUND SENTENCE STRUCTURES

Learn the following acronym:

For
And
Nor
But
Or
Yet
So

(Please see handbook for list of correlative coordinating conjunctions; these are punctuated the same as you would punctuate coordinating conjunctions not in pairs.)

OPTIONS: In compound sentence structures, you must join (not separate) one independent clause to another in one of three ways to avoid comma splices and fused (run-on) sentences:
First, you may use a comma with a coordinating conjunction (see above).
Second, you may join two independent clauses with a semicolon.
Third, you may join two independent clauses with a semicolon along with a conjunctive adverb followed by a comma.  Examples follow:

1.	The students enrolled in summer courses, and they soon longed for more leisure time.
2.	The students enrolled in summer courses; they soon longed for more leisure time.
3.	The students enrolled in summer courses; however, they soon longed for more leisure time.

A comma splice occurs when you omit the coordinating conjunction:
The students enrolled in summer courses, they soon longed for more leisure time.

A fused sentence (run-on) occurs when you omit EITHER the comma or the conjunction:
The students enrolled in summer courses they soon longed for more leisure time.
The students enrolled in summer courses and they soon longed for more leisure time.

Reminder: COORDINATING CONJUNCTIONS (cc) are markers of grammatical equivalency--i.e., nouns, verbs, phrases, independent clauses, et cetera:

1.	She bought sugar and flour (simple sentence, compound nouns functioning as direct objects).
2.	She left the store in a rush and then returned to work (simple sentence, compound predicate).
3.	She bought sugar and flour, and then she returned to work (compound sentence structure).

CONJUNCTIVE ADVERBS are not markers of equivalency, however.  Instead, they are common transitional expressions that assume a different name when placed between two independent clauses in a compound sentence.  In this position, they serve only to strengthen the relationship between the two independent clauses; they do not, to repeat, function as grammatical equalization.  Note the following example of the omission of the semicolon and the resulting error:

Comma splice: The students enrolled in summer courses, however, they soon longed for more leisure time.
Corrected: The students enrolled in summer courses; however, they soon longed for more leisure time.

You will also benefit from memorizing the following most commonly used conjunctive adverbs:
therefore, hence, moreover, thus, then, still, however, besides, likewise, otherwise, accordingly, consequently, furthermore, nevertheless, in addition, as a matter of fact, in fact, as a result, et cetera.  Remember: These words function as transitional expressions when they enjoy other positions in the sentence besides between two independent clauses.

Memorizing the following patterns of correctly punctuated compound sentences will enable you to avoid writing fused (run-on) and spliced sentences: 

Independent clause, cc independent clause.
Independent clause; independent clause.
Independent clause; ca, independent clause.

Should you elect to use a conjunctive adverb, always follow it with a comma.  Please note: Using a conjunctive adverb is always optional, not mandatory.

Similarly, whenever you use transitional expressions that fall within the body of a sentence, use commas before and after transitional expressions:

Example: The student enrolled in summer courses; they soon longed, however, for more leisure time.

COMPLEX SENTENCE PATTERNS

Comma splices and fused sentences cannot occur in complex sentence patterns.  Do memorize, however, the correct punctuation patterns below:

Dependent clause, independent clause (use comma following introductory dependent clause).
Independent clause dependent clause (no comma).