apostrophe: plurals

Certain plurals are sometimes written with ’s:

• abbreviations whose appearance would otherwise be ambiguous or confusing, and the plurals of lower-case letters, symbols and numerals:

• c.o.d.’s
• POW’s
• SIN’s
• x’s
• a’s and w’s
• +’s and -’s (pluses and minuses)
• 6’s (or 6s)

• cited words:

an overabundance of is’s and which’s

Note: It is not necessary to use the apostrophe in set expressions such as “the dos and don’ts,” “no ifs, ands or buts,” “the whys and wherefores.”

• words not conveniently pluralized:

• all the Toms, Dicks, Harrys and Louis’s
• all the Lao’s in Laos