Scientific writing 3.0: A reader and writer's guide - Jean-Luc Lebrun, Justin Lebrun 2021

Topic sentences
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The reading toolkit

As we’ve seen, topics come upfront in a sentence and often introduce the subject of that sentence. What if you wanted to introduce the topic of not just one sentence, but one whole paragraph?

Black opals are extremely rare gemstones, making them highly sought after (and highly priced) in gem markets.

What do you think will be covered in the subsequent paragraph? It could go into the rarity of black opals, their value in the gem market, or even just more general exciting facts about black opals. The sentence creates a very strong expectation that we will more deeply explore the topic of the sentence at length. This type of sentence is called a topic sentence.

Topic sentences always appear at the beginning of a new paragraph, and are fantastic ways to guide the reader’s expectations over a longer period of time.