One of the foundational lessons is grammar is that of a/an. When does that mysterious little n jump out of the woodwork and grip itself steadfastly on the right side of that a? As most of the internet will not be able to tell you, it is whenever the first letter of the following word is a vowel or vowel sound (e.g an eon or an hour).
Example: That is an operating system, an OS if you will.
However, you will notice something that sentence assumes, namely the pronounciation of acronyms. Some people would read OS aloud as "operating system", some would read it as "Oh-Es" and others just "Aus". This leads to the following confusing sentence.
Example: I wrote a FAQ on the Legend of Zelda.
Nothing wrong with this sentence, save for potential eternal wrangling over proper grammar. Now, I am no expert grammarian but my instincts here lead be to believe there is a problem. A problem coming from the acronym "FAQ".
Some people will say aloud "Frequently Asked Questions" but those are very few because of the great mouthful that is, so most will default to either "Fak" or "Ef-Ay-Kyew". Therein is the problem.
"Fak" is a distinct consonant, while "Ef-Ay-Kyew" sports a vowel sound at the beginning. This creates a very real and confusing dichotomy between whether we should use a or an.
Anyone who prefers "Fak" is going to read that sentence and be perfectly content and happy, barring a complete failure at basic grammar and spelling. However, people who prefer "Ef-Ay-Kyew" will twitch when they reach "a FAQ" because as far as they can tell the author screwed up in the attempted sentence.
What results is an impossible situation wherein any perfectionist writer aware of the problem will be forced to refer to all such acronyms in the definitive or else risk going insane.
The problem consonants are as follows:
F - Ef
H - Aych
L - El
M - Em
N - En
S - Es
X - Ex
Many acronyms starting with this letters will cause great issues for writers. Thankfully a large number lend themselves almost fully to one pronouciation or another (MADD would very rarely be pronounced "Em-Ay-Dee-Dee" while NAACP would almost never be pronounced "Naspa" or "Nakp") or are large organizations requiring definitives.
As it stands, FAQ is probably the worst and singularly common case of an acronym commonly used by the public which exemplifies this problem.
Now that I've ruined the word for all you grammatical perfectionists out there (I know I've sent some of you into seizures), I can rest for the day satisfied with a job well done, if overly verbose.