An in-text citation is the brief marker placed in the body of a document at the exact point where a source is used; the reference list is the full set of entries at the end that the markers point to. A citation system is the disciplined pairing of these two halves — a short signal in the text and a complete record at the back — so that any reader can move from a claim to its source and back again.
The two halves are designed for different jobs. The in-text marker is kept minimal so it does not disrupt reading. The reference entry is kept complete so retrieval never fails. Neither works alone: a marker with no entry is a dead end, and an entry with no marker is an orphan.
The two halves of a citation system
Every mainstream citation system is built from the same pairing, even though the surface format differs:
- In-text citation — an author–date marker such as (Okafor, 2020) or a numeric marker such as [7], sitting beside the borrowed material.
- Reference list entry — the full bibliographic record, carrying author, year, title, container and a persistent identifier so the source can be located.
This is the structural backbone described in our explainer on what a citation is.
Author–date systems
Author–date systems — used by APA and the author–date variant of Chicago — place the author surname and year of publication in the text. The reader matches that surname to the alphabetised reference list. A page number is added for direct quotations.
For example, an in-text marker of (Okafor, 2020, p. 14) maps to a reference list entry beginning Okafor, A. (2020). Because the list is alphabetised, the reader scans to “O” and finds the full record. The strength of this system is that the reader sees author and date without leaving the sentence, which signals currency and authority inline.
Numeric systems
Numeric systems — Vancouver, used across medicine and many sciences under ICMJE conventions — replace the author–date marker with a number assigned in order of first appearance. The reference list is ordered numerically to match. An in-text marker of [7] sends the reader to the seventh entry in the list.
Numeric markers keep the running text uncluttered, which suits papers with very many references. The trade-off is that the reader cannot tell who or when from the marker alone — they must turn to the list.
Worked example: the same source, two systems
| System | In-text marker | Reference list entry (schematic) |
|---|---|---|
| APA 7 (author–date) | (Okafor, 2020) | Okafor, A. (2020). Title of work. Publisher. https://doi.org/… |
| Vancouver (numeric) | [1] | 1. Okafor A. Title of work. Publisher; 2020. Available from: https://doi.org/… |
Note how the data elements — author, year, title, publisher, DOI — are identical; only the order, punctuation and the form of the in-text marker change. That stability of elements beneath varying surface format is the central insight of comparing citation styles.
How markers map to entries
The integrity of a citation system depends on a clean one-to-one mapping. Every in-text marker must have exactly one matching reference entry, and — in a reference list, as opposed to a fuller bibliography — every entry must correspond to at least one in-text marker.
- No orphan entries. A reference with no in-text marker suggests background reading that belongs in a bibliography, not a reference list.
- No dangling markers. An in-text citation with no matching entry leaves the reader unable to retrieve the source.
- Consistent identifiers. Author names should be disambiguated — an ORCID iD resolves the “which J. Smith?” problem — and persistent identifiers such as DOIs should resolve.
Maintaining this mapping is also a matter of research integrity: a broken link between marker and entry undermines the verifiability that citation exists to provide.
Choosing and applying a system
Discipline usually dictates the choice: author–date for the social sciences and humanities, numeric for medicine and many natural sciences. Whatever the system, the rule is consistency — apply one set of conventions throughout, and let a reference manager enforce the marker-to-entry mapping for you. Practical guidance for getting this right lives in our resources for authors.
Frequently asked questions
What is the difference between an in-text citation and a reference?
An in-text citation is the brief marker in the body of the text. A reference is the full entry in the reference list that the marker points to. They are two halves of one citation: the marker signals where a source is used, and the entry lets the reader retrieve it.
How do numeric and author–date systems differ?
Author–date systems put the author surname and year in the text and alphabetise the reference list. Numeric systems use a number assigned in order of first appearance and order the list to match. Numeric markers are more compact; author–date markers show authorship and currency inline.
Should every reference list entry have an in-text citation?
Yes, in a reference list. A reference list contains only sources actually cited, so every entry should map to at least one in-text marker. Background reading that was not cited belongs in a bibliography instead.
Where can I check standardised definitions of these terms?
The CASRAI dictionary provides standardised definitions, and our comparison of citation styles shows how different systems format the same source.