Now, you know what a paragraph is, right? We all read them and write them. However, it's important that we're all on the same page so we can move on to a more in-depth look at how they work. Therefore, a paragraph is a collection of sentences within a piece of writing, connected by a single focusing idea.
In academic essays as opposed to fiction, for example, a strong paragraph spans several sentences, but tackles only one central idea. That being said, there's no such thing as the correct number of sentences in a paragraph, but a paragraph can be too long or too short. It all depends on what they're supposed to do for the writing project.
Breaks between paragraphs are used as places to rest while reading -- places to process what is read, and to prepare to continue on through the text. Therefore, it should make sense that not giving your readers enough of these breaks will hurt your essay's readability, even if you don't change a word in it.
That being said, having paragraphs that are too short is also usually a problem. Again, there's nothing inherently bad about them, but short paragraphs are often a sign of either an incompletely developed idea, or that one fully realized paragraph has been arbitrarily divided into two. For readers, too-short paragraphs can be overlooked amongst longer ones; or when they come in numbers, they can create a jittery, jarring reading experience, which is arguably just as bad as having no paragraph breaks at all. Besides, if the purposes of a paragraph are to have a central claim and to support it, then a paragraph should be long enough to do both.
Like the sentences in a paragraph, there is no correct number of paragraphs for an essay, as the number should reflect the needs of the text itself and the author's goals, which are always going to vary from text to text and from person to person.
In order to discuss more clearly the form and function of a paragraph, it's important to discuss its key parts. Nothing is more central to an academically-sound paragraph than its topic sentence. This is the sentence that most clearly expresses the thesis of a paragraph. In many ways, the paragraph is like a miniature essay, and like an essay, a paragraph's thesis often comes at or near the beginning. It is often, but by no means always, the topic sentence that starts a new paragraph, with all the rest following it as support.
Having focused paragraphs with solid topic sentences helps to anchor readers within the text and make it easier for them to absorb the writer's ideas rather than having to pay attention to how those ideas are being displayed. For the writer, having focused paragraphs with solid sentences is also useful, as during the revision and editing process it's easier for the writer to look at each paragraph and see whether or not the single idea it articulates supports the main thesis of the essay. This question is much easier to answer -- whether yes or no -- when the paragraph itself is clearly focused.
Now, if a topic sentence is the central thesis of the paragraph, what does that make all the other sentences? In composition, they are referred to as supporting sentences. These are the sentences in a paragraph that support its thesis, or main idea. In this way a paragraph is, again, like a miniature essay.
When writing, it's important to pay attention to what each supporting sentence is contributing to the paragraph as a whole. It's equally important to cut, change, or relocate irrelevant sentences -- any that don't do enough to support the thesis -- even if they are interesting or relevant elsewhere, or for other purposes.
Next, let's take some time to look at a couple paragraphs to see how topic and supporting sentences can, and sometimes cannot, work together. Read the paragraph below, and as you do, look for the topic sentence and any supporting sentences.
Commensalism is the name for a biological interaction in which one organism benefits and the other derives neither benefit nor harm. In a stable environment -- like that which occurs in isolated environments -- organisms evolve to lose anything that isn't necessary to their daily needs. But when that environment changes, when the organisms upon which others depend can no longer survive, entire ecosystems can crash. Though much less commonly known than the related terms of parasitism and symbiosis, commensalism is common when multiple species live together in non-predator-prey relationships.
So, what did you find? The topic sentence should have been fairly clear. The first sentence, at least, seems to be one. But what about the second? It doesn't really seem to be supporting the first -- or at least, not very well. Also, the third sentence seems to be more supporting of the second sentence than the first, so perhaps that's the topic sentence. The fourth and last sentence is definitely a supporting sentence, or perhaps it could be its own topic sentence in some other paragraph.
In any case, if, as you were reading this, you got a little confused, don't worry. This paragraph was chosen as an example because it demonstrates fairly well what happens when a paragraph doesn't have a clearly stated central topic. This one seems to have two, or maybe even three. The writer would certainly benefit from a little revision time, and should probably work a little harder to make sure he or she knows exactly what this paragraph wants to say and why.
Let's look at another paragraph, one that won't cause so much confusion. It contains some fairly complex ideas, so take your time reading it. It is an excerpt from an essay titled Reconstruction, by Frederick Douglass, the writer, social reformer, statesman, and escaped slave.
There is cause to be thankful even for rebellion. It is an impressive teacher, though a stern and terrible one. In both characters it has come to us, and it was perhaps needed in both. It is an instructor never a day before its time, for it comes only when all other means of progress and enlightenment have failed. Whether the oppressed and despairing bondman, no longer able to repress his deep yearnings for manhood, or the tyrant, in his pride and impatience, takes the initiative, and strikes the blow for a firmer hold and a longer lease of oppression, the result is the same: society is instructed, or may be.
This paragraph, while full of complicated ideas and a nuanced approach to them, should still have been easier to grasp. Did you find the topic sentence? It's the first sentence of the paragraph. You can hopefully see how every other sentence in the paragraph supports it, either by explaining why we should be thankful, or going into detail as to what about rebellion gives us cause to be grateful. Did you notice the slightly circular form here, how the first ("It is an impressive...") and last ("society is instructed...") supporting sentences seem to come back around to the same point? By the end, we readers are in a much better position to appreciate why or how rebellion is a good teacher. As mentioned above, the paragraph is like a miniature essay, almost self-contained in this case.
Finally, let's look at one more paragraph -- a very different, and in many ways, much simpler, paragraph -- but one that should also help demonstrate how topic and supporting sentences can work together.
During the months that followed the Japanese bombing of Pearl Harbor, everything changed for Hawaii. Martial law was declared and the radio carried stories of internment camps forming in California, though of course no general was dumb enough to try that in the islands. Japanese women stopped wearing their kimonos to the market anyway, and even my great grandmother, descendant of Irish farmers that she was, began keeping her own kimono, a gift from a former maid, in the back closet.
Here, again, the first sentence is the thesis, where it works as one. Even though the paragraph is much more narrative, the argument it makes in its topic sentence -- that everything changed -- is supported by the information contained in all the rest of the sentences. Whether historical, cultural, or personal, we're still being given supporting evidence about the change, even though it is a relatively narrative piece.
Now that you've seen three different ways sentences can interact in a paragraph, you should be in a better position to read other paragraphs and to write your own.
Source: Adapted from Sophia Instructor Gavin McCall