The handling of abbreviations can be tricky, especially if you have to use different style guides for different types of writing. Some guidelines only permit abbreviations in tables or reference sections. Other guidelines are more lenient but their requirements can still differ in significant ways. Here are pointers about a few of those differences. I’ll use three stylebooks for examples.

Abbreviations for Professional Titles
Stylebooks often disagree on when to abbreviate certain professional or political titles. For example, the Chicago Manual of Style (CMS) states that certain titles such as “Senator” should be spelled out when only the surname will be used but abbreviated before the full name, for example:

Sen. Benjamin Cardin
Senator Cardin

The Associated Press (AP) Stylebook approves using the abbreviated version of “Senator” before one or more names in regular text, but requires that the title be spelled out in a direct quotation:

Sen. John Doe addressed his colleagues.
“Senator John Doe should run for a second term,” stated the analyst.

Yet another stylebook, Words into Type, declares that the title should never be abbreviated except when used in a table.

Abbreviations for Names of Months
With AP style, you only use abbreviated month names when they are being used along with a specific date. Plus, only certain months can be abbreviated: Jan., Feb., Aug., Sept., Oct., Nov. and Dec.

The CMS and Words into Type dictate that month names should always be spelled out in text.

All three stylebooks approve of abbreviating the month names in tabular formats. In such a case, the AP stylebook recommends abbreviations consisting of the first three letters of each month. The CMS and Words into Type follow that same format except for May, June and July, which remain unabbreviated. If space limitations require that even those months be shortened, both stylebooks offer this abbreviating option:

January = Ja
February = F
March = Mr
April = Ap
May = My
June = Je
July = Jl
August = Ag
September = S
October = O
November = N
December = D

Time of Day
AP requires that the common abbreviations for morning and afternoon to be lowercased with periods: a.m. and p.m. The CMS prefers that you use small capitals and the periods are optional. Words into Type prefers small caps with periods and no spaces, but allows for either lowercase or full case (both with periods).

These are just a few of the differences you can encounter when writing abbreviations, so it is always a good idea to check the relevant stylebook for proper usage guidelines. Remember that abbreviations are generally never used in very formal writing, and even when you’re writing in a format that allows you to snip words, avoid letting your copy look like alphabet soup.