Yes, you cite the same source every single time you use it — every quote, every paraphrase, every borrowed idea. The full author-date information appears the first time; after that, APA and MLA accept a short form (author last name plus page or year). Ibid. is a Chicago-only convention and only works for two or more consecutive citations of the exact same source.
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The instinct to cite a source only once to avoid looking repetitive is wrong. Every piece of information that is not yours, and not common knowledge, needs a citation every time it appears. The shortcut is in the form of the citation, not the frequency.
APA 7: cite every time, shorten after first
APA uses parenthetical author-date format. The first time you reference a source, include author and year. Every subsequent time, use the same author-date pair. There is no shortened form beyond removing first names (APA never uses first names inline) and no ibid.
First citation: "Previous studies have shown that sleep loss impairs memory consolidation (Walker, 2017)."
Second citation, same paragraph: "This effect is strongest when deprivation exceeds 24 hours (Walker, 2017)."
Direct quote, needs a page number: "Walker (2017) describes sleep as 'the greatest legal performance-enhancing drug' (p. 107)."
If you cite the same work multiple times in the same paragraph without another source in between, APA 7 allows you to drop the year on the second reference within the same paragraph: "Walker (2017) argues that sleep is foundational to memory. Walker further shows that REM phases are particularly critical." But the moment another source appears, reset to the full author-date.
MLA 9: short form after first full citation
MLA uses parenthetical author-page format. The first time, it is (Author Page). Every subsequent use is also (Author Page), which is already short. If you mention the author by name in the sentence, drop the name from the parenthetical: "Walker argues sleep is foundational (107)."
If you cite two works by the same author, distinguish them by adding a short title: (Walker, Why We Sleep 107) versus (Walker, "The Sleep-Learning Link" 23). For our deeper look at when you need page numbers specifically, see page numbers in citations.
Chicago: ibid. only for immediately consecutive citations
Chicago (notes-bibliography) uses footnotes. The first footnote is the full citation; subsequent notes use short form (Author, Short Title, page).
Ibid. (Latin: "in the same place") appears only when the immediately previous footnote is the exact same source. If any other note intervenes, you must use the short form.
First note: 1. Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams (New York: Scribner, 2017), 107.
Second note, immediately after, same source: 2. Ibid., 112. or the modern preference 2. Walker, Why We Sleep, 112.
Third note, different source: 3. Randall Munroe, Thing Explainer (Boston: Houghton Mifflin, 2015), 45.
Fourth note, back to Walker: 4. Walker, Why We Sleep, 120. (Do NOT use Ibid. here — note 3 broke the chain.)
The Chicago Manual of Style 17th edition actively discourages ibid. in favor of the short form because short forms survive reordering and editing.
Quick reference table
| Scenario | APA 7 | MLA 9 | Chicago | | --- | --- | --- | --- | | First citation | (Walker, 2017) | (Walker 107) | Full footnote | | Second citation, same paragraph | (Walker, 2017) or (Walker) | (Walker 108) | Short form or ibid. (if consecutive) | | Direct quote | (Walker, 2017, p. 107) | (Walker 107) | Short form with page | | Two works by same author | (Walker, 2017, 2020) | (Walker, Why We Sleep 107) | Short form with distinguishing title | | After another source intervenes | (Walker, 2017) again | (Walker 110) | Short form (no ibid.) |
What you never do
- Cite once at the end of a paragraph that uses a source in three sentences. Every borrowed sentence needs its own citation.
- Use "(same)" or "(as above)" casually. These are not accepted abbreviations in any style.
- Drop the citation because "it is obvious I am still using the same source." Your reader should never have to guess whether a sentence is yours or borrowed.
- Use ibid. in APA or MLA. Ibid. is a Chicago/Turabian convention; both APA and MLA just use the short author-date form.
Paraphrase vs. quote: citation is the same
Whether you are paraphrasing or quoting directly, you still cite. The difference is page numbers: direct quotes always need them; paraphrases need them in APA and MLA when you are citing a specific passage. For a paraphrase that summarizes an entire work, the year or author alone is usually enough — details in our page numbers in citations note.
If your source has three or more authors, see et al. when to use for the exact rule per style.
For the full formatting picture, see our research paper guide. And for a full citation workflow with examples pulled automatically into the right format, you can start on our citation page.
Frequently asked questions
Can I cite a source once for an entire paragraph?
No in APA and MLA. Each sentence built on borrowed information needs its own citation. The exception is a paragraph explicitly announced as summarizing one source ("Walker's 2017 study established three findings"), where you can cite at the start and clarify the scope. Even then, most graders prefer repeated citation.
Is using ibid. in APA wrong?
Yes. APA does not use ibid. Use the short author-date form every time.
How do I cite two papers by the same author from the same year?
Add a letter after the year: (Walker, 2017a) and (Walker, 2017b). The reference list entries carry the matching letters.
Do I have to cite common knowledge?
No. Facts like "water boils at 100 degrees Celsius at sea level" do not need citations. The test: is this information easily findable in multiple general sources? If yes, it is common knowledge. When in doubt, cite.