What term refers to a word or phrase that links different ideas in writing?

The term that refers to a word or phrase that links different ideas in writing is "transition." Transitions are essential tools in writing because they help guide readers through the text, indicating relationships between concepts or sections. They clarify the flow of ideas, allowing the writer to seamlessly connect thoughts, emphasize points, or contrast differing viewpoints. By using transitions, writers enhance coherence and improve the overall readability of their work, making it easier for readers to follow the progression of ideas.

While the other options might convey a similar notion of relationship—connection and linkage denote the act of joining together, while association suggests a relationship between ideas—they do not capture the specific function of facilitating the flow of text as precisely as "transition" does. Transitions serve a distinctive role in indicating shifts or continuities between sections of writing, which is why it is the most appropriate term in this context.