Grammar Tip – a.m. and p.m.

BizWritingTip reader: “I noticed in your last tip that you used a.m. instead of AM. Was there a reason for this?”

BizWritingTip response: According to both the Oxford Canadian Dictionary and The Canadian Press Stylebook, the designations for morning and afternoon are written in the lowercase with periods between each letter.

Examples

10 a.m.

3:15 p.m.

Note: There is a space between the number and the abbreviation.

In some print documents, you can use small capitals (small caps) – A.M. and P.M. – if you have that option. However, avoid the use of all-capital letters.

Examples

10 A.M. (incorrect — large caps)

10 A.M. (correct – small caps)

3:15 P.M. (incorrect – large caps)

3:15 P.M. (correct —small caps)

Don’t use AM. This is the abbreviation for “amplitude modulation.” Its most common use is with radio stations.

I trust this BizWritingTip provides you with timely information.