There are some abbreviations and acronyms that are so familiar to us that we don’t even know what they stand for. You’ve probably heard of NASCAR, but have you heard of the National Association for Stock Car Auto Racing? And do you curse the IRS or the Internal Revenue Service during tax season?
Here are two that you probably see, use or at least think about every day: a.m. and p.m. Unlike many abbreviations, they are lowercase, and the periods help minimize confusion, though people will still probably know what you mean if you type “10am.”