Topic Sentence

A topic sentence states the main idea of a paragraph. It performs two functions: it tells the reader what the paragraph is about (the topic) and what the writer's point about that topic is (the controlling idea). Together, these define the paragraph's scope — everything that follows should develop, illustrate, or support the topic sentence.

Position

The topic sentence most commonly appears first in the paragraph, functioning as an advance organiser. This is the default position in academic writing and the position learners should master first. However, it can also appear:

• Last — The paragraph builds up evidence or examples and concludes with the main point (inductive pattern)
• First and last — The main idea is stated, developed, then restated or refined
• Implied — No single sentence states the main idea explicitly (common in narrative and journalistic writing, but not recommended for L2 academic writers)

For ELT purposes, teach the first-position topic sentence as the default. Other positions can be introduced at upper-intermediate and advanced levels.

What Makes a Good Topic Sentence

A good topic sentence is:

• Specific enough to be developed in one paragraph — "Transport is important" is too vague; "Public transport reduces urban air pollution in three key ways" gives a clear, manageable scope
• General enough to require development — "The bus costs $2.50" is a fact, not a topic sentence
• Arguable or informative — It makes a claim or identifies a point worth developing

Teaching Topic Sentences

Activities

1. Match topics to controlling ideas — Given topics and controlling ideas separately, learners combine them into effective topic sentences
2. Choose the best topic sentence — Given a paragraph, select the most appropriate topic sentence from three options
3. Identify the controlling idea — Underline the part of the topic sentence that limits the paragraph's scope
4. Write topic sentences from prompts — Given a paragraph topic, write a topic sentence that includes a clear controlling idea
5. Paragraph coherence check — Given a topic sentence and several possible supporting sentences, select only those that develop the controlling idea

Common Student Problems

• Too broad — "Education is important." This could fill a book, not a paragraph.
• Too narrow — A fact with no room for development. "My school has 500 students."
• Topic without controlling idea — "I will discuss technology." This names a topic but does not commit to a point about it.
• Multiple ideas — "Social media causes loneliness and governments should regulate it." Two separate paragraphs compressed into one sentence.

Topic Sentences and Essay Structure

In a well-structured essay, topic sentences serve as the connective tissue between the Thesis Statement and the body paragraphs. Each topic sentence should clearly relate back to the thesis while introducing one distinct aspect of the argument. Reading just the thesis statement and the topic sentences of each body paragraph should give a coherent summary of the essay's argument.