Differentiate between "prompt engineering" and "prompt design." Are these terms interchangeable?

The terms overlap and many people use them interchangeably, but when a distinction is made, prompt design is the craft of writing a prompt (wording, structure, examples, format) and prompt engineering is the wider discipline of building, testing and running prompts reliably in a system (evaluation, versioning, retrieval, tools, monitoring and cost).

Prompt design

• Writing clear instructions for a specific task.
• Choosing a role, tone and audience.
• Structuring the prompt with sections and delimiters.
• Selecting and writing examples.
• Specifying the output format.
• Iterating on wording by looking at outputs. It is close to writing and communication: the skill of giving a capable reader an excellent brief.

Prompt engineering Everything in design, plus:

• Success criteria and evaluation: test sets, graders, metrics, regression testing.
• System architecture: prompt chains, routing, retrieval-augmented generation, tool definitions, agents.
• Context engineering: deciding what information enters the context window at each step.
• Parameters: model choice, sampling settings, structured outputs.
• Operations: templates, version control, logging, monitoring, prompt caching, cost and latency.
• Security and safety: defending against prompt injection, output validation, guardrails.
• Maintenance: re-testing when models change.

An analogy Prompt design is like writing a good function; prompt engineering is like software engineering: tests, architecture, deployment and maintenance around the function.

Example Designing a prompt that summarises customer calls well is prompt design. Building the system that transcribes thousands of calls, retrieves the account history, runs the summary prompt, validates the JSON, measures summary quality against a reviewed set, tracks cost and alerts on drift is prompt engineering.

Are they interchangeable? In everyday conversation, yes, mostly. In job descriptions and team roles, "prompt engineer" usually means the broader, technical role, while "prompt design" is used more often in content, UX and conversation design contexts. In an interview, acknowledge the overlap, give the distinction, and show you can do both: write clear prompts and prove with evaluation that they work.