Building Topic Sentences That Preview the Paragraph

A topic sentence has one job that's easy to state and surprisingly easy to miss under exam pressure: it should let a reader predict, in general terms, what the rest of the paragraph is about to say. That sounds like an obvious requirement, but a huge share of Task 2 paragraphs open with a sentence that announces a subject without committing to any actual claim about it — and the two are not the same thing. "There are several reasons for this trend" names a subject (reasons for a trend) but commits to nothing specific; a reader finishing that sentence has no idea what's coming next beyond the vague category of "a reason." This distinction between naming a topic and making a claim about it is exactly what separates a weak topic sentence from a strong one, and it's commonly overlooked precisely because the weak version isn't grammatically incorrect — it simply isn't doing the job a topic sentence exists to do.

The consequence of getting this wrong compounds across an entire essay. A paragraph that opens with a vague, subject-only topic sentence forces the reader to read the whole paragraph before understanding its point, rather than being oriented from the first sentence — and an examiner reading quickly, as examiners genuinely do, relies heavily on topic sentences to track an essay's overall logical structure. If every topic sentence in an essay is a vague gesture toward a subject rather than a specific claim, the essay can feel structurally thin even when the underlying ideas inside each paragraph are actually reasonable, simply because the organisational signposting that should carry the reader through the argument isn't there.

A strong topic sentence, by contrast, states an actual, specific claim: "One significant reason for this trend is the growing availability of affordable technology." Notice what this version does that the vague version doesn't — it names a specific cause (affordable technology), and it signals that the paragraph will now explain and support that specific claim. A reader who has only read this one sentence can already predict, roughly, what's coming: an explanation of how affordable technology relates to the trend, probably with an example. That predictive power is the actual test of whether a topic sentence is doing its job, and it's a test you can apply to your own writing directly — read only the topic sentence, then ask what you'd expect the rest of the paragraph to contain, and check whether the paragraph actually delivers that.

There's a related trap worth naming separately: a topic sentence that isn't vague but instead over-delivers, compressing the entire paragraph's content into one sentence rather than merely previewing it. A topic sentence that already states the specific example, the specific reasoning, and the specific conclusion leaves the rest of the paragraph with nothing left to do except repeat what's already been said in slightly different words. The right scope for a topic sentence sits between these two failure modes — specific enough to commit to an actual claim, but general enough that the paragraph's remaining sentences still have real work to do developing, supporting, and illustrating that claim with reasoning and a concrete example.