A citation is a pointer from a statement to the source that supports it — the evidence behind a claim, made explicit so a reader can check it for themselves.
The word carries two related meanings.
In academic writing
A citation is a formal reference to a prior work: a book, paper, or page that a claim draws on. It does two jobs — it credits the original author, and it lets a reader trace an assertion back to its origin and judge whether it holds up. A good academic citation is precise enough to find the exact source, not just gesture at it.
In AI
In document AI, a citation is a pointer from a generated claim to the specific passage in the source that supports it. When a model summarises a PDF or answers a question about a wiki page, each sentence it produces should be traceable to real text it actually read — not to its training data, and not to a plausible-sounding guess.
Why AI citations must be verifiable
A citation is only worth as much as the checking it enables. A reference that points at "the document" in general, or worse, at a passage that doesn't actually say what the claim says, is decoration — and decorative citations are exactly how AI hallucinations slip past readers. A verifiable citation, by contrast, lets you click through to the precise sentence and confirm the claim with your own eyes.
That means a real AI citation should:
- point to an exact passage, not a whole page or file;
- be machine-checkable, so unsupported claims can be caught and dropped;
- take you straight to the source rather than asking you to go hunting.
Sidenote builds every answer this way. Responses are grounded in retrieved passages, each claim carries a citation that scrolls to and highlights the source, and any claim that can't be matched to a passage has its citation dropped before you see it. See how it works on the Citations feature page.