English Grammar Review
Special Topics


Abbreviations save ink when writing and save time when talking. Saving ink or space is important when we prepare detailed tables and when we format our text in narrow columns. Saving time when we talk is natural simply because we don't like wasting time. For example, employees and contractors of NASA say, "NASA," much more often than they say, "National Aeronautics and Space Administration."

There are many rules for using abbreviations. Let's explore four categories:


Rule: Do not follow an acronym with a word that is part of the acronym.

At 12:45 GMT time, Uanhenga sent the CD disc. Using his PIN number, he accessed the LAN network.

At 12:45 GMT, Uanhenga sent the CD. Using his PIN, he accessed the LAN.

Rule: To form the plural of most acronyms, add s to the end. Do not use an apostrophe.

He sent a package of CDs as well as a list of PINs for each of the LANs.

Rule: When first using an acronym, define it by spelling it out once; then be consistent in how you refer to the term.

Assemble the uniform resource locator (URL). Attach name/value pairs to the uniform resource locator and send it back to the server.
[not consistent]

Assemble the uniform resource locator (URL). Attach name/value pairs to the URL and send it back to the server.


The use of the period is sometimes pivotal in using an abbreviation correctly. For example, PO stands for purchase order but P.O. stands for post office.

Rule: The abbreviation for a single word should end with a period.

Mr. Antero Ningi Jr. from Luanda Corp. ordered misc. supplies on Wed. last week in Angola.

Note: English includes a variety of shortened forms of words that are not followed by a period.

The app helped me prep in the lab on the specs for the promo that had no typos.

Rule: Most abbreviations for multi-word phrases that use lower-case letters use periods but no space in between.

Mr. Xitu delivered it f.o.b. at 8 a.m., i.e., at the start of the work day.

Rule: Abbreviations for academic degrees use a period after each element and no space in between.

Ms. Abreu earned her B.S. five years ago and her R.N. this year.


In nontechnical writing, units of measure are usually spelled out.

It was a 12-kilometer journey to Lubango for the 20-liter container.

In technical writing, units of measure are usually abbreviated.

Rule: When they are accompanied by a numerical value, units of measure are commonly abbreviated without periods and are often the same for singular and plural.

   yd - yard, yards
   m - meter, meters

   lb - pound, pounds
   gm - gram, grams

   gal - gallon, gallons
   L - liter, liters

   s - second, seconds
   min - minute, minutes

Rule: When describing a set or range of numbers, use an abbreviation only with the last number.

The office included a 5 x 9 ft closet. It was full of 2, 6, and 12 L containers.

Rule: In general, larger units of time should not be abbreviated when accompanied by a numerical value: day (d), week (wk), month (mo), year (yr). Smaller units of time should be: hour (h), minute (min), second (s).

Design took 10 years. Approval took 11 months. Setup took 12 weeks. Calibration took 13 days. But the experiment was completed in 14 h 15 min 16 s.

Note: Abbreviations for units of time can vary by technical discipline or by style guide. For example, some communities use hr for hour and hrs for hours.

Special characters

Rule: The characters @ and & normally are surrounded by spaces.

We should order 100 @ $25 from Marks & Spencer.

Rule: The characters % and # (pound) normally are not preceded by a space when they are put in back of a number.

We'll have 80% of the 50# paper we need.

Rule: The characters $ and # (number) normally are not followed by a space when they are put in front of a number.

We will save $950 if we reorder #8375.

Lesson: Abbreviations
Module: Special Topics
Course: English Grammar Review