alum

1 of 3

noun (1)

al·​um ˈa-ləm 

1

: a potassium aluminum sulfate KAl(SO₄)₂·12H₂O or an ammonium aluminum sulfate NH₄Al(SO₄)₂·12H₂O used especially for its astringent and styptic properties

2

: any of various double salts isomorphous with potassium aluminum sulfate

3

: aluminum sulfate

alum

2 of 3

noun (2)

ə-ˈləm 

: alumnus, alumna

a Yale alum

alum

3 of 3

abbreviation

aluminum

Did you know?

Is it acceptable to use alum for alumnus or alumna?

The words that we have used to refer to people who have attended or graduated from a school, college, or university have changed a bit over the past several centuries. Traditionally, the word alumnus has been used to refer to a single male, whereas alumna has been used for a single woman. Initially the plural forms were alumni to refer to multiple men (or multiple men and women) and alumnae for multiple women. A little over a hundred years ago the shortened form of alum began to be used to describe a graduate or past attendee of either gender. Although many people feel that alum is informal, it is in increasing use, and we appear to be moving toward a greater acceptance of the word. The plural of alum is alums.

Examples of alum in a Sentence

Recent Examples on the Web

Noun

On Wednesday, April 10, the Gossip Girl alum, 36, gushed about Ryan Reynolds’, 47, while sharing the trailer for his upcoming movie IF on her Instagram Stories. —Gabrielle Rockson, Peoplemag, 11 Apr. 2024

The Greek auteur has again put together a jaw-dropping supporting cast, including Poor Things alums Willem Dafoe and Margaret Qualley, alongside Jesse Plemons, Hunter Schafer, Joe Alwyn, Hong Chao and Mamoudou Athie. —Scott Roxborough, The Hollywood Reporter, 11 Apr. 2024

The Girl Meets World alum is one of several artists slated to perform at both weekends of this year’s festival, which will be headlined by Lana Del Rey, Doja Cat and Tyler, the Creator as well as feature a reunion concert from No Doubt. —Hannah Dailey, Billboard, 9 Apr. 2024

Both presidents subsequently resigned from their positions after widespread condemnation from Jewish communities nationwide, alums, and students. —Emma Colton, Fox News, 7 Apr. 2024

University of Michigan alum Raoul Wallenberg was born in Sweden and educated in Paris and at U-M before serving as a diplomat across World War II-era Europe. —Detroit Free Press, 5 Apr. 2024

This house-turned-museum was once the home of Dr. Manassa Pope, a Shaw University Medical School alum and prominent doctor. —Tykesha Spivey Burton, Essence, 5 Apr. 2024

Levin, an economist, Stanford alum and member of President Joe Biden’s Council of Advisors on Science and Technology, takes charge on Aug. 1. —Ethan Baron, The Mercury News, 4 Apr. 2024

Plus, every female secretary of state in U.S. history was a Girl Scout or Girl Guide alum, including Madeleine Albright, Condoleezza Rice, and Hillary Clinton. —Rachel Ventresca, Fortune, 30 Mar. 2024

Word History

Etymology

Noun (1)

Middle English, from Anglo-French alum, alun, from Latin alumen

Noun (2)

by shortening

First Known Use

Noun (1)

14th century, in the meaning defined at sense 1

Noun (2)

1877, in the meaning defined above

Kids Definition

alum

noun

al·​um

ˈal-əm

1

: either of two colorless crystalline compounds containing aluminum that are used in medicine (as to check local sweating or to stop bleeding)

2

: aluminum sulfate

Medical Definition

alum

noun

al·​um ˈal-əm 

1

: either of two colorless or white crystalline double sulfates of aluminum used in medicine internally as emetics and locally as astringents and styptics:

a

: one KAl(SO₄)₂·12H₂O that is a sulfate of aluminum and potassium

called also potassium alum

b

: one consisting of an ammonium aluminum sulfate NH₄Al(SO₄)₂·12H₂O

called also ammonia alum, ammonium alum

2

: any of various double salts isomorphous with potassium aluminum sulfate