Apostrophes

As you already know, apostrophes are used to form both contractions—two words collapsed into one—and possessives. Handily, we can virtually ignore the issue of contractions here, since they are so easily understood and are rarely used in technical writing. With possessives, the apostrophe is used, typically in combination with an "s," to represent that a word literally or conceptually "possesses" what follows it. The apostrophe is also used for general terms to indicate the singular possessive case.

Examples of Singular Possessives

• a student's paper
• the county's borders
• a nation's decision
• one hour's passing
• miner's inch
• author's revisions

Apostrophes with Words Ending in "s"

Although practices vary, for words that already end in "s," whether they are singular or plural, we typically indicate possession simply by adding the apostrophe without an additional "s."

Examples

• Presidents' Day
• Student Affairs' Office
• Mars’ atmosphere
• interviewees’ answers

Apostrophes with Acronyms and Numerals

In technical writing, acronyms are frequently pluralized with the addition of an "s," but there is no need to put an apostrophe in front of the "s" when your intention is simply to pluralize rather than show possession. When referring to decades, form the plural by adding an "s," but do not use the apostrophe.

Plural Forms: Correct vs. Incorrect

Correct

• SSTs
• the 1960s
• she is in her 30s

Incorrect

• SST's
• the 1960's
• she is in her 30's

When numerals or letters serve as the name of something and an "s" is needed, use an apostrophe before the "s" to make it clear that the letters are not part of the name.

Names Ending in Letters or Numerals

Correct

• Boeing 747's
• mind your p's and q's

Incorrect

• Boeing 747s
• mind your ps and qs

When Possessives Are Implied Without the Apostrophe

Convention and frequency of usage sometimes dictate that the apostrophe is dropped. In proper names that end in "s," especially geographic locations, academic institutions, and government entities, the apostrophe is often omitted. Likewise, in everyday combinations and acronyms where possession is automatically understood or contextually irrelevant, the apostrophe is not needed.

Examples Where the Apostrophe is Omitted

• United States government
• Hells Canyon
• Veterans Highway
• Harpers Ferry
• mens room
• Johns Hopkins University
• an FDA regulation
• the NIOSH position
• the Virginia legislation
• an 1860 law