Acronyms and initialisms are like the trick or treaters who show up at our doors on Halloween. We THINK we know what each kid is supposed to represent — a princess, a ghost, a skeleton — but sometimes we're not so sure. A monster? A pirate? A scarecrow?

Similarly, whenever we encounter an unfamiliar acronym or initialism, our self-confidence is MIA and we often experience FOMO.

Fear not! Here are some handy FAQs about these tricksters.

Q: What's the difference between an acronym and an initialism?

A: Acronyms are pronounced as one word, e.g., FOMO (Fear Of Missing Out), NATO (North Atlantic Treaty Organization).

Initialisms are pronounced as a sequence of letters, e.g., MIA (Missing in Action), CIA (Central Intelligence Agency), NSA (National Security Agency).

Q: Are acronyms always capitalized?

A: Certain acronyms have become so common that they're now written entirely in lowercase letters: laser (Light Amplification by Stimulated Emission of Radiation), scuba (Self-Contained Underwater Breathing Apparatus) and sonar (SOund NAvigation Ranging).

There's a growing tendency to write familiar acronyms of more than three letters with only the first letter capitalized, e.g., Nimby (Not In My BackYard), Nasdaq (National Association of Securities Dealers Automated Quotations).

A few acronyms appear in both uppercase and lowercase forms: EPCOT/Epcot (Experimental Prototype Community Of Tomorrow). Short initialisms are often rendered as lowercase letters, e.g., i.e., r.p.m., m.p.h., p.m. and, yes, e.g. itself, especially when they might be confused with an actual word, such as am/a.m.

Q: Should each letter in an acronym be followed by a period?

A: Usually not, but there's a lot of variation on this. Many short, lowercase initialisms, such as the ones I just cited, have periods. The Associated Press Stylebook, for instance, recommends the use of periods in most two-letter abbreviations (B.A., B.C., U.N., U.K.), along with Ph.D., but not in ID, EU or its own initialism, AP.

Q: How do you form the plural of an acronym?

A: Most are formed by simply adding a lowercase "s," e.g., FAQs (Frequently Asked Questions), Navy SEALs (SEa Air Land forces).

But when adding an "s" alone causes confusion or makes the word look strange, place an apostrophe before the "s," EDS's not EDSs (Electronic Data Systems), AWACS's, not AWACSs (Airborne Warning And Control Systems).

Now you can get back to hosting those TOTs (Trick Or Treaters).

Rob Kyff, a teacher and writer in West Hartford, Connecticut, invites your language sightings. His new book, "Mark My Words," is available for $9.99 on Amazon.com. Send your reports of misuse and abuse, as well as examples of good writing, via email to WordGuy@aol.com or by regular mail to Rob Kyff, Creators Syndicate, 737 3rd Street, Hermosa Beach, California, 90254.

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