rubber puzzles with colorful alphabets

Abbreviations (those are the shortened forms of words) can be difficult to understand. Only use them if you know that your readers will understand them. You might even like to spell them out the first time you use them in an email or letter if you really want to use them later in the text.

Instead of …                   write …
approx.                             approximately or about
asap                                 as soon as possible
BTW                                 by the way
DIY                                   do it yourself
Fyi                                    for your information
HQ                                    headquarters
max.                                  maximum
min.                                   minimum
24/7                                   24 hours a day, 7 days a week