1. Abbreviation

An abbreviation is a shortened form of a word or phrase. It usually involves cutting down the word by omitting some letters.

Examples:

• Dr. for Doctor
• Jan. for January
• etc. for et cetera

Abbreviations can take various forms—some end with a period, some don't.

2. Acronym

An acronym is a special type of abbreviation formed from the first letters of a phrase, and it's pronounced as a word.

Examples:

• NASA — National Aeronautics and Space Administration (pronounced "nasa")
• UNICEF — United Nations International Children's Emergency Fund (pronounced "you-ni-cef")
• SCUBA — Self-Contained Underwater Breathing Apparatus (pronounced "scoo-ba")

3. Initialism

An initialism is also formed from the first letters of a phrase, but each letter is pronounced separately, not as a word.

Examples:

• FBI — Federal Bureau of Investigation (pronounced "F-B-I")
• CPU — Central Processing Unit (pronounced "C-P-U")
• ATM — Automated Teller Machine (pronounced "A-T-M")

Summary:

Term	Formed from	Pronounced as	Example
Abbreviation	Shortened word or phrase	As the shortened word	Dr., etc.
Acronym	First letters of phrase	Like a word	NASA, SCUBA
Initialism	First letters of phrase	Letters separately	FBI, CPU