Learn English – Acronym of abbreviation for “At the time of writing this document”

An acronym (as the term is commonly used) is a term that is formed from the initial letters of some longer name and is pronounced differently than the expanded form. Examples of acronyms as the term is commonly used:

• FBI, which stands for Federal Bureau of Investigation, but is pronounced ef-bee-I
• NATO, which stands for North Atlantic Treaty Organization, but is pronounced NAY-toe
• IUPAC, which stands for International Union of Pure and Applied Chemistry, but is pronounced I-U-pak

An abbreviation is written differently from the expanded form but is pronounced the same. Examples:

• Mr., which stands for mister and is pronounced mister
• ft., which stands for feet and is pronounced feet
• etc., which stands for et cetera and is pronounced et cetera

Whether the form is pronounced as a “word” or as letter names or as some combination of the two is a red herring. The key difference is whether the abbreviated form is pronounced differently from the expanded form.

The simple answer is, you can't. If you are having a conversation with someone who uses an acronym, the only way you'd know is if they spelled out the letters. Otherwise, you'd simply have to ask. And obviously used in written form such as an e-mail, you'd never know if it were an acronym outside of context. Though a good list can be found here.

A good rule of thumb is that acronyms that might look difficult to sound out are likely spelled instead (FBI, FDA, IBM to name a few).