An analogy is an extended comparison between two things that are unlike in most respects but similar in the respect that matters for the writer’s purpose. Where a metaphor identifies (“grief is an ocean”), an analogy explains (“grief is like an ocean in that it comes in waves — sometimes calm, sometimes overwhelming, and you can’t control which”).
Analogy is the primary tool for making unfamiliar things understandable in terms of familiar ones. It is essential in technical writing, where the writer must bridge the gap between the reader’s existing knowledge and the new concept. “A database index works like a book index: instead of reading every page to find a topic, you look up the topic in the index and go directly to the right page.” The reader who understands book indexes now has a mental model for database indexes.
Analogy also serves essay writing, where it can make abstract arguments concrete. An essayist arguing that social media platforms function as public utilities might compare them to telephone systems — both are infrastructure that people depend on, both have natural monopoly characteristics, both raise questions about public regulation of private systems. The analogy doesn’t prove the argument, but it gives the reader a framework for understanding it.
The danger of analogy is overextension. Every analogy breaks down at some point — the two things being compared are, after all, different things. A database index is not a book index: it’s maintained automatically, it can be queried computationally, and it has performance characteristics that book indexes don’t. The writer’s responsibility is to use the analogy where it illuminates and abandon it before it misleads. Pushing an analogy past its useful range confuses rather than clarifies.
Related terms
- imagery — analogy works through concrete, sensory comparison
- exposition — analogy is a tool for exposition, making complex ideas accessible
- cognitive load — analogy reduces cognitive load by connecting new concepts to existing knowledge