Now that we know more about writing sentences, let’s start considering what to do with those sentences. Whether you’re writing a book, a speech, an email, or something else, odds are you need to write more than one sentence. If those multiple sentences are all about the same topic, you’re writing a paragraph.

How long should a paragraph be? The number of sentences in a paragraph can vary depending on your purpose for writing, but the rule of thumb is that a single paragraph should contain between 3-5 sentences. More than that, and you should consider breaking the group up into multiple paragraphs. The guidelines I am about to set forth are most relevant to expository writing, but still contain useful information for other types of writing.

Think of a paragraph as being like a sandwich. The top piece of bread is the topic sentence; it introduces the main idea of the paragraph. Do not begin your topic sentence with the phrase “This paragraph is about.” Aside from the lack of creativity involved in such wording, your goal with a topic sentence is not just to introduce the topic, but to also share your specific argument or perspective. For example, if I were to write about why cats make good pets, my topic sentence could be something like “There are many benefits to choosing to have a cat as a pet.” My topic is clear: cats; my perspective, that cats make good pets, is also apparent.

The fillings of the sandwich are the supporting sentences. In these sentences, you will provide facts, examples, evidence, etc. that support the main idea of the topic sentence. To continue my example, I could support my perspective that cats make good pets with the following: “Cats are relatively low-maintenance; they do not require walks or grooming and are easily house-trained. Due to their small size and lack of need for a backyard, they are very apartment-friendly. Additionally, their innate prey drive helps reduce the number of household pests such as mice or bugs.”

The bottom slice of bread is the concluding sentence; this sentence wraps up the topic, reinforcing the main point, and if there is another paragraph following it, it can act as a transition. Since I have not been planning on writing multiple paragraphs about why cats make good pets, it would be perfectly acceptable for me to conclude my paragraph with the sentence “There are few other pets that offer such advantages.”

I would like to reiterate that a single paragraph should focus on a single concept. My example paragraph is about the benefits of having a cat; if I were to start talking about how cute and cuddly they are, or to compare them to other types of pets, those would be different concepts. Trying to cram too many ideas together leads to walls of text, and no one wants to read a wall of text.

In addition to sticking to one topic, you also want your paragraph to be coherent. You don’t want your sentences to feel like a random list; the use of transition words helps guide the reader from one sentence to the next. To add information, use words like additionally and furthermore. For showing contrast, employ words like however or the phrase “on the other hand.” To show a result, use words like therefore or consequently.

One final tip: it helps to read your paragraphs out loud to yourself. If you run out of breath, your sentences are probably too long. If it feels awkward, work on your transitions. Reading your writing out loud can also help you catch typos and other errors.