Apostrophes and Contractions

An apostrophe takes the place of missing letters in a contraction and is also used to indicate the omission of the first two numbers of a year:

We'll never forget the ice storm of '97.

Though we use contractions quite frequently when speaking or when writing an informal message or email, in academic writing, the best advice is to avoid using contractions unless you are intentionally trying to create a relaxed, informal tone for effect. Be aware that many professors object to the use of contractions in any kind of formal writing. Use "cannot" instead of "can't" or "does not" instead of "doesn't," for example. Don't sound too colloquial in your prose unless you know your breezy, conversational style will be well received.

Special uses of the apostrophe

The apostrophe also has a number of special uses when combined with individual letters, numbers, and symbols.

Currently, there are two practices in book and magazine print for indicating plurals of single letters, abbreviations, numbers, and symbols. The older style uses the 's in all instances; the newer style avoids the apostrophe and simply adds an s except where confusion might result—when adding the s unintentionally results in a word. The newer style is preferred, reserving the apostrophe for indicating possession and contraction.

• With letters:

three Bs and a C+
two APCs
NGOs
but
the Oakland A's
Irwin with two i's (since A's and i's can be confused with the words As and is)

• With numbers:

  either CF-18's or CF-18s
  1900s or 1900's
  but
  the class of '05

• With symbols:

  +'s and -'s and &'s