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Answer: Punctuation should aid reading and prevent misreading; if it does not clarify the text, omit it. In a series of three or more words, phrases, or figures, put a comma after each member.

GPO

• Well-planned word order requires a minimum of punctuation.
• The adopted style must be consistent and based on sentence structure.
• Examples: "red, white, and blue"; "horses, mules, and cattle."

Digital.gov

• It can be confusing to omit the Oxford comma, so the guide errs on the side of caution.
• Use your best judgment: if anything is unclear, clarify it.

See also

• plain-colon-capitalization
• plain-list-punctuation-consistency

Claims

• id: C1 claim: GPO: punctuation that does not clarify should be omitted. source: S1 evidence: "If it does not clarify the text it should be omitted"

• id: C2 claim: GPO: punctuation should aid reading. source: S1 evidence: "Punctuation should aid reading and prevent misreading."

• id: C3 claim: GPO uses the serial comma in a series of three or more. source: S1 evidence: "After each member within a series of three or more words, phrases,"

• id: C4 claim: Digital.gov leans toward keeping the Oxford comma. source: S2 evidence: "we’d like to err on the side of caution"

Sources

• [S1] GPO Style Manual (2016), Chapter 8: Punctuation. U.S. Government Publishing Office (govinfo). https://www.govinfo.gov/content/pkg/GPO-STYLEMANUAL-2016/pdf/GPO-STYLEMANUAL-2016-10.pdf . License: US government work, public domain. Accessed 2026-11-09.

• [S2] Digital.gov style guide. Digital.gov (GSA). https://digital.gov/style-guide/ . License: US government work, public domain. Accessed 2026-11-09.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted). Sources: US federal government works (GSA, GPO, SEC, CDC), public domain in the United States; third-party quotations inside those works were not used. Text was condensed and changed from the originals.

@misc{iil_note_y02vyn11,
  author = {{iinventedlight}},
  title = {{Punctuate to prevent misreading: the serial comma}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-09},
  url = {https://iinventedlight.com/library/notes/plain-serial-comma-for-clarity/},
  note = {Permanent ID iil:note:y02vyn11. License: CC-BY-4.0.},
}

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