As requested,
Understanding Run-On Sentences (and Comma Splices)
A 'run-on sentence' is a sentence which involves two or more independent clauses that aren't joined by appropriate conjunctions or punctuation. I'll try my best to break those concepts down in an easy to understand fashion.
Independent Clause
An independent clause is basically a sentence that makes sense on its own. In its simplest form, an independent clause will contain at least one noun (a 'thing') followed by at least one verb (an 'action'). In lah-dee-dah posh grammar speak these are referred to as a 'subject' (the thing the sentence is about, and the thing that's 'doing' the verb) and a 'predicate' (the bit of the sentence that modifies the thing the sentence is about) respectively. A quick test of whether something's a dependent/subordinate or independent clause is to separate it from your longer, potentially run-on, sentence and see if it makes sense on its own. For instance:
"The fire engine was red and was used to douse the blaze."
What parts of the above example might be a clause? Well, it can't be the 'and' because 'and' is a conjunction (a word used specifically to join two clauses or words). This means it's got to be the stuff around the 'and', so these are our two clauses:
"The fire engine was red"
"was used to douse the blaze."
So which of these two sentences is the independent clause? Are they both independent clauses? To find out, we apply our noun+verb (subject-predicate) rule:
"The fire engine was red": Has both a subject noun (fire engine) and a verb (was). We can tell that the noun in this case is the subject of the verb because it's doing the verb i.e. it's being red.
"was used to douse the blaze.": Has two verbs (was used, to douse) and one object noun (the blaze). We can tell the noun in this case is the object of the verb because it's affected by the verb i.e. it's receiving a dousing.*
We can now see that the first sentence makes sense on its own. It's not very informative, but it does make sense; the subject of the sentence (the doer in the sentence which should be introduced prior to the verb, or it results in passive voice**) is being modified by the verb. Conversely, our second sentence doesn't have a subject at all; it has an object (the blaze) which is being affected (doused) by an unknown subject (? was used). We can see now that our second sentence doesn't make sense at all without reference to the first sentence, so our second sentence isn't an independent clause: it is a subordinate clause (a clause which helps to provide more information about the independent clause, but can't stand on its own).
Joining Independent Clauses
So how, and why, might we join two independent clauses? We might want to join two independent clauses when we want to relate two separate, but interdependent, concepts to one another. For instance, consider the following sentence:
"It was a balmy summer's night, the clouds dreamily crawled across the sky."
This is a comma splice (a run-on sentence), so called because we've taken two independent clauses and just shoved them together with no appropriate conjunction. If we examine the sentence above, we can see there are two independent clauses with one on each side of the comma:
"It was a balmy summer's night" subject pronoun (It) + verb (was)
"the clouds dreamily crawled across the sky." subject noun (the clouds) + verb (crawled)
A comma can't be used to join two independent clauses; that's simply not its function. Commas can be used in a vast number of ways, but cramming together independent clauses isn't one of them. Many ways in which a comma can be used are described
here (but it's by no means a full list).
So what can we do? We want to link the ideas in both independent clauses, but we don't want to seem like a lazy writer! We have a couple of ways of turning our run-on sentence into a bona fide sentence:
1) Use a semicolon
Semicolons are the brooding, misunderstood punctuation. They're used for a number of reasons, but chief amongst them are uses that link two thematically linked independent clauses and uses that link the items in a complex list (a list whose members contain commas). Solution:
"It was a balmy summer's night; the clouds dreamily crawled across the sky."
Here's where we've got to be careful not to overuse semicolons: semicolons can't directly follow one another as punctuation. For instance, if we were to add a third independent clause:
"It was a balmy summer's night, the clouds dreamily crawled across the sky, the fairground ride's lilting lullaby filled the crowd with excitement."
Then it wouldn't be acceptable to just add a third sequential semicolon:
"It was a balmy summer's night; the clouds dreamily crawled across the sky; the fairground ride's lilting lullaby filled the crowd with excitement."
Instead we'd have to find another piece of punctuation or a conjunction!
Really, the criteria for the use of a semicolon should be a slightly more direct relationship between the two independent clauses, but I couldn't think of a particularly good example.
2) Use a conjunction preceded by a comma
A conjunction is a FANBOYS word:
For
And
Nor
But
Or
Yet
So
It is used to link two things together, and that includes independent clauses! When we link two independent clauses together with a conjunction, it is proper to precede the conjunction with a comma as so:
"It was a balmy summer's night, and the clouds dreamily crawled across the sky."
As with the semicolon, we shouldn't keep this string of conjoined independent clauses going with a comma and conjunction (it's not strictly
wrong, but it just sounds awful): eventually we're going to need some different punctuation like...
3) Make them separate sentences
It's also perfectly acceptable to just use a standard fullstop to turn them into two separate sentences. After all, they're both independent clauses and can stand on their own merits:
"It was a balmy summer's night. The clouds dreamily crawled across the sky."
*For those of you who need further explanation about the concept of subjects and objects of a verb, here's an addendum (if you need to clear up your understanding of nouns and pronouns then head to the final point***):
Subjects and Objects
The subject of a verb will typically be introduced before the verb (unless the writer is using the passive voice), and the object will typically be introduced after the verb.
The subject can be thought of as the 'doer' of the verb: the noun in a sentence that's carrying the verb out. For instance:
"He ran"
Is a simple independent clause in which the pronoun (He) is the one doing the verb (ran). Note that, as this uses active voice**, the subject is appearing in the clause before the verb. In an active voice sentence, this is a pretty handy way of telling who the subject of the verb is: it's the noun that comes first! However, in this example it's pretty obvious which noun is the subject because there's only the one noun! Consider the following:
"He ran the application"
Here we've got two nouns ('He' and 'the application'), so we've got to decide which is the subject of the verb and which is the object. Who's the doer? Well, 'He' is the doer because he's the one that's affecting 'the application', namely by causing it to run. 'the application' is the object because it's being affected by him, namely it's being caused to run.
**For those of you who'd like to learn more about active and passive voice
Active vs Passive Voice
Active voice occurs when the subject of a transitive verb (a verb with a direct object) appears before the verb and the object after the verb; passive voice is vice versa. For instance:
"Charlie fired upon the stranger" - Active voice
"The stranger was fired upon by Charlie" - Passive voice
Active voice gives a sense of urgency to the clause and shifts the focus of the clause onto the protagonist. Passive voice places the focus of the clause on the verb's object. At this point, it's worth noting that some editors and professors consider passive voice a serious grammatical editor regardless of the use. This stance is actually incorrect when used in the following ways (it's a form of hypercorrection):
1) When you want to emphasise the object
"Marcus was struck by the stupidity of the comment" -Passive voice
Here we're choosing to use passive voice because the part of the clause which actually interests us is the effect the verb (and its subject) are having upon our protagonist, Marcus. We're not interested in the comment, we're interested in its effect upon Marcus, so we're actively choosing to put the object (Marcus) in the place where one would normally expect the subject to be.
"The stupidity of the comment struck Marcus" - Active voice
Here we end up focussing on the comment, but we're interested in what's going on with Marcus!
2) When you want to de-emphasis an unknown or unclear subject
"Jake was annoyed by his colleagues" -Passive voice
Here we've got a clear idea of who Jake is, but we don't have a clear idea of who his colleagues are, so we de-emphasis them by sticking them in the object position. It's not so much that we're trying to shift focus onto Jake, but rather that we're trying to shift focus away from the subject; a verb whose subject is quickly raised and then ditched might seem a little jarring.
"His colleagues annoyed Jake" - Active voice
Here we end up bringing focus to Jake's colleagues. That's going to be a little odd if this is the only time we ever hear about them.
3) When the subject is irrelevant to the reader
"Michael was taught grammar" - Passive voice
Here we don't need to know who actually taught Michael grammar because it just isn't relevant to the reader, so we choose to leave the subject of the verb out of the clause and shift Michael up to the subject position.
"Mister Jones taught Michael grammar" - Active voice
Here we end up introducing unnecessary information, namely that Michael's grammar teacher was Mister Jones. The reader doesn't need to know anything about who taught Michael grammar, so throwing in this reference just to clear up the passive voice only ends up distracting from the actual plot.
*** Here the differences and uses of nouns and pronouns will be covered:
Nouns and Pronouns
To quickly clear up some terminology, a noun is a word that can act as a subject or an object of a verb. Nouns typically refer to places, things, people or concepts. A pronoun is a word that stands in a noun's stead in a sentence, so that we don't have to continuously retype a noun. Consider:
"Claire had a pair of shoes"
Here, both 'Claire' and 'shoes' are nouns. They're the subject and object respectively of the verb 'had', and they both refer to 'a thing'. We can stick pronouns in their place and the sentence still makes sense:
"She had a pair of those"
Here the pronoun 'She' replaces 'Claire' and 'those' replaces 'shoes'. If we'd previously declared nouns which could obviously be represented by those pronouns, then we'd be justified in using pronouns instead of just retyping the nouns over and over again. So why might we use a pronoun instead of a noun, given the chances for a pronoun-laden sentence to become confusing? Simply put, because an over abundance of nouns can sound horrid:
"Claire had a pair of shoes, and Claire loved her shoes. Claire's shoes were a bright red with pretty little bows glued to the tongues, and Claire's shoes shone with polish."
Uses no pronouns, but we end up hearing 'Claire' and 'shoes' continuously. If we were to declare 'Claire' and 'shoes' and then start using pronouns, we'd get a much better flow:
"Claire had a pair of shoes, and she loved them. They were a bright red with pretty little bows glued to the tongues, and they shone with polish."
Remember, though: Always make sure you've clearly declared your nouns before you start replacing them with pronouns, and if you've got more than one noun in place that could be represented by a given pronoun then make sure you're clearly differentiating between each use!
Some people may argue that, upon first read through, the reader will know that the person didn't eat his gran, but I'd use the comma anyway, for clarification.
