Abbreviation is shortening words - acronyms and initialisms are forms of abbreviation. An example of abbreviation would be saying misc for miscellaneous, or writing Dr. for doctor. There are some that are very standard, and sometimes you can get away with shortening a word and it still being understood even if it is non-standard! Acronyms are using the first letters in a phrase to make a word you say - like scuba (self-contained underwater breathing apparatus) or NATO (North Atlantic Treaty Organization). Initialisms are similar to acronyms except you say the letters individually. For example, with MIA (Missing in Action) you say the letters M-I-A instead of "Mia". All of these things fall under the category of abbreviations.

Abbreviations are shortened words in English. For example M.I.A. - Missing In Action. E.T.A. - Estimated Time of Arrival. Some texting words are abbreviations too. LOL - Laughing Out Loud. BRB - Be Right Back. Things like that ^^