Decoder. plain-English AI glossary

Delimiter

● Core

Special characters or markers that separate different sections of a prompt — user input from instructions, one example from another.

Think of it like

Using <----> to mark where one paragraph ends and the next begins.

Example

Prompt: "Instructions: ...\n\n### INPUT\nUser query here\n\n### OUTPUT\nExpected format" — the ### marks section boundaries.

How it actually works

Delimiters reduce ambiguity. They signal to the model where parsing should change. Common delimiters: newlines, ```, ###, tags (<input>, </input>). They're especially useful when input contains special characters that might confuse the model.

For product teams

Improves reliability when input is noisy or adversarial.

For engineers

Choose a delimiter unlikely to appear in user input. Document it in your prompt template. Use consistently.

Structured output — Part of structured output design.

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