Abbreviations and initialisms are both ways of shortening words, but they’re not the same thing. The difference comes down to how they’re formed and how they’re said.

An abbreviation is a shortened form of a single word or phrase. It keeps part of the original—either the start, the end, or sometimes a mix. Ave. for Avenue is a clear example.

An initialism is a specific type of abbreviation made from the first letters of several words. Each letter is pronounced separately—FBI for Federal Bureau of Investigation, for instance.

Both save space and time, but you use and pronounce them differently.

Using “Abbreviation”

You use abbreviation when a word or phrase is shortened yet still keeps part of its full form. Abbreviations appear in addresses, notes, and everyday speech—anywhere you want a more compact version of a term.

Examples:

  • Rd. is an abbreviation for Road.
  • In medical charts, HR is shorthand for heart rate.
  • Writing “hrs” for hours is a common abbreviation in schedules.

Using “Initialism”

An initialism condenses a phrase into its first letters. Each letter is said on its own, unlike an acronym where you speak it as a single word. You’ll often see these in business, tech, and government because full names can get long.

Examples:

  • HR is the initialism for Human Resources.
  • HBO stands for Home Box Office.
  • CD-ROM—short for Compact Disc Read-Only Memory—has been around for decades.

Definitions, Parts of Speech, and Pronunciation

Abbreviation

  • Meaning: Shortened form of a word or phrase that leaves out letters or syllables. Often ends with a period.
  • As a noun: “St.” is the abbreviation for “Street.”
  • Pronounced: /əˌbriː.viˈeɪ.ʃən/

Initialism

  • Meaning: Letters taken from the start of each word in a phrase, pronounced individually.
  • As a noun: “UN” stands for “United Nations.”
  • Pronounced: /ɪˈnɪʃ.ə.lɪ.zəm/

Quick Takeaway

Abbreviations shorten a word but keep some of its letters. Initialisms use only the first letters from a group of words—and you read each letter out loud. The difference sounds small, but it changes how you write and speak them.