Plurals of Acronyms and Abbreviations
To form the plural of an acronym or other abbreviation, simply add s to the end. No apostrophe is necessary.
- URL/URLs
- WAN/WANs
- DVD/DVDs
- PC/PCs
- HDD/HDDs
- FAQ/FAQs
- MD/MDs
- EMT/EMTs
- PhD/PhDs
- MBA/MBAs
- CEO/CEOs
- VP/VPs
- VIP/VIPs
- ATM/ATMs
- ISBN/ISBNs
- MNC/MNCs
- PSE/PSEs
- REIT/REITs
- NGO/NGOs
- SSN/SSNs
![Plurals of abbreviations: Rules and examples. To form the plural of an abbreviation, simply add "s." No apostrophe is needed (URLs, CEOs, PCs, PDFs, ATMs, PhDs). For abbreviations ending in an "S" sound, add "s" or "es" (CMSs or CMSes, PBXs or PBXes). Don't add "s" to abbreviated SI units (10 kg, not 10 kgs; 10 ml, not 10 mls). For contracted titles, add "s" and move the period to the end (Drs. Who and Strange, Profs. Curie and Spivak, Mss. [or Mses.] Curie and Spivak, but Messrs. Who and Strange [formal/legal usage]).](https://editorsmanual.com/wp-content/uploads/2022/05/plurals-of-abbreviations-media-768x432.webp)
An apostrophe before the s that forms the plural is not incorrect but generally omitted in formal writing.
- URLs or URL’s
- LANs or LAN’s
- CEOs or CEO’s
- PhDs or PhD’s
Plurals of abbreviations ending in S
An acronym or abbreviation that ends in an S sound can be pluralized either by adding s as usual or by adding es. Avoid inserting an apostrophe.
- CMSs or CMSes
both pronounced see-em-ess-es
- SMSs or SMSes
- DNSs or DNSes
- PBXs or PBXes
Stay consistent in usage across a document.
Plurals of abbreviated units of measurement
Symbols for units of measurement do not have a separate plural form: don’t add an s to form the plural of an SI or other metric unit.
- 5 kg (five kilograms), not 5 kgs
- 10 g (grams)
- 10 cm (centimeters)
- 50 ml (milliliters)
- 10 s (seconds)
- 100 m (meters)
- 300 ms (milliseconds)
Not adding s to form the plural of a unit of measurement helps avoid ambiguity: otherwise, “100 ms” could be either 100 meters or 100 milliseconds.
Units of time (seconds, minutes, hours, months, and years) are often written with an added s to construct the plural form. This is considered acceptable in nontechnical, nonacademic writing. The period at the end is optional.
- 10 secs.
- 60 mins.
- 24 hrs.
- 12 mos.
- 300 yrs.
Plurals of abbreviated titles like Dr. and Mr.
To form the plural of a contracted social or professional title, simply add s and move the period to the end.
- Drs. Who and Strange are at the door.
- We interviewed Drs. Keyland and Murphy.
- Profs. Curie and Spivak are my idols.
- Revs. Johnson and Obayi addressed the congregation.
- We have spoken with Sens. Williams and Garcia.
- Govs. Brown and Russo both refused to sign the bill into law.
The plural form of Mr. is Messrs. (an abbreviation of the French messieurs). It is now seen only in formal and legal writing.
- Messrs. Brown and Green signed the contract today at 2 p.m. EST.
The plural of Mrs. is Mmes. (for the French mesdames), now used in English only for humorous effect.
- Mmes. Brown and Green have arrived uninvited for tea, or perhaps to inspect our new furniture.
The title Ms. in the plural becomes Mss. or Mses.
- Mss. Roy and Desai write books for a living.
In British usage, periods (or full stops) are omitted in contracted forms (e.g., Mrs Green, Mr Brown, Drs Jones and Smith).
Plurals of shortened forms
Shortened forms such as Vol. (for volume) and Ed. (for editor) take an s to form a plural. The period goes after.
- Vols. 3–7
- Robinson & Keating (Eds.)
Convention dictates that in reference lists, the plural form of the abbreviation p. (page) is pp. (pages), not ps. Also, the abbreviation trans. (for translator) does not change in the plural.