(Oxford, Noun). Abbreviation is a shortened form of a word or phrase: SKU is the abbreviation for Stock Keeping Unit. Acronym: (Oxford, Noun). Acronyms are words formed from the initial letters of other words and pronounced as they are spelled, not as separate letters. Examples include: "Aids" is the acronym for acquired immune deficiency syndrome, "NATO" is the acronym for North Atlantic Treaty Organization, "UNESCO" is the acronym for United Nations Educational, Scientific, and Cultural Organization, and "SIM (card) " is the acronym for subscriber identification module. Most acronyms can be written as capital letters or with only an initial capital letter. Some acronyms are so established that they are now 'normal' words, generally used without conscious awareness of their original full form. These words should be written in lower-case letters. Examples include: laser acronym for light amplification by stimulated emission of radiation, radar acronym for radio detection and ranging, quango acronym for quasi-autonomous non-governmental organization, and scuba acronym for self-contained underwater breathing apparatus