Differ and vary both describe differences, so their meanings overlap. The best choice often depends on what you want to emphasize: a comparison or a pattern of change.
Differ means to be different from someone or something. Use it when comparing people, things, or situations. The pattern differ from introduces what you are comparing something with.
- This year’s schedule differs from last year’s.
- The two bags differ in size.
The second example uses differ in to name the feature that is different. You can compare more than two things, too: “The five apartments differ in layout.”
Vary often describes change or differences across times, places, or members of a group. It is useful when something is not the same in every case.
- The temperature varies throughout the day.
- Delivery times vary from two to five days.
Common patterns include vary by, vary with, and vary from … to …. For example, “Hotel rates vary by season” explains what the differences depend on.
Sometimes either verb works: “The rooms differ in size” and “The rooms vary in size” are both natural. The first emphasizes comparison; the second suggests a range of sizes. This is not a strict rule about two things versus many, or fixed differences versus changes over time. Choose the verb that best matches your focus and the sentence pattern you need.