Top Definitions
Quiz
Related Content
Alum Vs. Alumnus Vs. Alumni Vs. Alumna Vs. Alumnae
Examples
British
Medical
Scientific

alum

[ al-uhm ]

/ ˈæl əm /

Save This Word!

noun Chemistry.

Also called potash alum, potassium alum. a crystalline solid, aluminum potassium sulfate, K2SO4⋅Al2(SO4)3⋅24H2O, used in medicine as an astringent and styptic, in dyeing and tanning, and in many technical processes.

one of a class of double sulfates analogous to aluminum potassium sulfate, as aluminum ammonium sulfate, having the general formula R2SO4⋅X2(SO4)3⋅24H2O, where R is a univalent alkali metal or ammonium, and X one of a number of trivalent metals.

(not in technical use) aluminum sulfate.

QUIZ

TAKE JOY IN ACING THIS QUIZ ON “PRIDE” SYNONYMS

Hold your head up high as you embark on this quiz that explores some of the synonyms and meanings of “pride.”

Question 1 of 7

What does "dignity" mean?

showing self-respect

treating others with kindness

acting selfishly

TAKE THE QUIZ TO FIND OUT

Origin of alum

First recorded in 1275–1325; Middle English <Anglo-French, from Latin alūmen; replacing Old English alefne, ælifnæ, from Old Welsh (compare Medieval Welsh elyf ) <Latin alūmini- (stem of alūmen )

Words nearby alum

alt text, Altus, ALU, aludel, alula, alum, alumin-, alumina, alumina cement, aluminate, aluminated

Other definitions for alum (2 of 3)

alum²

[ uh-luhm ]

/ əˈlʌm /

noun Informal.

an alumna or alumnus: Nearly 45 of us alums went on a day trip on the river to celebrate graduation.

Origin of alum

First recorded in 1875–80; by shortening

usage note for alum

See alumnus.

WORDS THAT MAY BE CONFUSED WITH alum

alum , alumna, alumnae, alumni, alumnus

Other definitions for alum (3 of 3)

alum.

abbreviation Chemistry.

aluminum.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022

ALUM VS. ALUMNUS VS. ALUMNI VS. ALUMNA VS. ALUMNAE

What’s the difference between alum, alumnus, and alumni?

The informal word alum refers to a graduate of a school, such as a high school or university. It’s a shortening of alumnus or alumna.

In Latin, alumnus specifically refers to a male graduate, and sometimes this distinction is carried into English, with alumna being used to refer to a female graduate. The plural of alumna is alumnae.

The plural of alumnus is alumni (which follows the plural ending construction used in other Latin-derived words, like stimulus and stimuli). Still, alumnus and alumni are both commonly used in a gender-neutral way.

Alum is also used regardless of gender. It’s sometimes pluralized as alums.

Here’s an example of alum and alumni used correctly in the same sentence.

Example: As an alum, you share something with all of the alumni, regardless of when each of you graduated.

Want to learn more? Read the breakdown of the difference between alumnus and alumni.

Quiz yourself on alum vs. alumnus!

True or False?

Alum and alumnus are both always used in a gender-neutral way.

How to use alum in a sentence

Natasha Strain, an alum of the campus who works as a childcare worker and supervisor at the facility, is one of the plaintiffs listed in the suit.
North County Report: San Pasqual Academy Supporters Sue to Stay Open|Kayla Jimenez|August 4, 2021|Voice of San Diego
For Top Chef, that meant many challenges that took advantage of outdoor kitchens, a bubble of all-star alums replacing the usual rotating cast of guest judges and a brand-new approach to viewers’ beloved Restaurant Wars.
Top Chef: Portland Was the Kindest Season Yet. Does the Finale Change That?|Elijah Wolfson|July 2, 2021|Time
She is currently a senior director at Fairmont Consulting Group, a boutique management consulting firm in the aerospace and defense sector founded by fellow alums Jay Wynn, MBA ’04, and Ben Harper, MBA ’08, SM ’08.
Meet the president: Annalisa Weigel ’94, ’95, SM ’00, PhD ’02|Nicole Estvanik Taylor|June 30, 2021|MIT Technology Review
In their MHS homes, alums said they were ranked by how well they did their chores and followed rules.
“I Finally Got to the Mountaintop and I Failed”|by Bob Fernandez, The Philadelphia Inquirer, and Charlotte Keith, Spotlight PA|June 10, 2021|ProPublica

Natasha Strain, an alum of the campus, works as a childcare worker and supervisor at the facility.
San Pasqual Academy Is Still Fighting for Its Life|Kayla Jimenez|May 10, 2021|Voice of San Diego
A TNR alum dives deep in what happened with the 100-year-old institution.
The Daily Beast’s Best Longreads, Dec 8-14, 2014|William Boot|December 13, 2014|DAILY BEAST
And those who take issue with the ice bucket challenge have found an unexpected spokesperson in Jackass alum Steve-O.
#IceBucketChallenge Wisdom From 'Jackass' Steve-O|Kevin Zawacki|August 21, 2014|DAILY BEAST
Marine friends, all ranks and all mostly Anbar fighting alum, have been sending me emails as well.
Their Fight…But Our Legacy: The New Battle for Fallujah|John Kael Weston|January 12, 2014|DAILY BEAST
Apple alum Tony Fadell reinvented the boring market for home thermostats with his sleek and eco-savvy digital Nest.
How to Hack the Perfect Home|Daniel Gross|November 15, 2013|DAILY BEAST
Petraeus, himself a Sosh alum, became the central figure for a mix of reasons.
The Petraeus Revolution: How He Changed the American Way of War|John Barry|January 8, 2013|DAILY BEAST
If they require a second water put alum to that also as well as to the rinsing and blue water.
The Ladies' Book of Etiquette, and Manual of Politeness|Florence Hartley
Thus the proportions are omitted, and alum becomes alum compound, whatever that may mean.
The Propaganda for Reform in Proprietary Medicines, Vol. 1 of 2|Various
On examination it was found that the enclosure of the Atarrea was broken down, and the source saturated with alum.
Travels in Peru, on the Coast, in the Sierra, Across the Cordilleras and the Andes, into the Primeval Forests|J. J. von Tschudi
The principal impurity, and one which renders alum unfit for the use of the dyer, is iron.
Cooley's Cyclopdia of Practical Receipts and Collateral Information in the Arts, Manufactures, Professions, and Trades..., Sixth Edition, Volume I|Arnold Cooley
The applications of alum in the arts and manufactures are numerous and important.
Cooley's Cyclopdia of Practical Receipts and Collateral Information in the Arts, Manufactures, Professions, and Trades..., Sixth Edition, Volume I|Arnold Cooley

British Dictionary definitions for alum

alum

/ (ˈæləm) /

noun

Also called: potash alum a colourless soluble hydrated double sulphate of aluminium and potassium used in the manufacture of mordants and pigments, in dressing leather and sizing paper, and in medicine as a styptic and astringent. Formula: K 2 SO 4 .Al 2 (SO 4) 3 .24H 2 O

any of a group of isomorphic double sulphates of a monovalent metal or group and a trivalent metal. Formula: X 2 SO 4 .Y 2 (SO 4) 3 .24H 2 O, where X is monovalent and Y is trivalent

Word Origin for alum

C14: from Old French, from Latin alūmen

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for alum

alum

[ ăl′əm ]

Any of various double sulfates of a trivalent metal such as aluminum or iron and a univalent metal such as potassium or sodium that are used as topical astringents and styptics.

Scientific definitions for alum

alum

[ ăl′əm ]

Any of various crystalline double salts of a trivalent metal (such as aluminum, chromium, or iron) and a monovalent metal (such as potassium or sodium), especially aluminum potassium sulfate. Alum is widely used in industry as a hardener and purifier, and in medicine as an emetic and to stop bleeding.

alum

Origin of alum

Words nearby alum

Other definitions for alum (2 of 3)

Origin of alum

usage note for alum

WORDS THAT MAY BE CONFUSED WITH alum

Other definitions for alum (3 of 3)

ALUM VS. ALUMNUS VS. ALUMNI VS. ALUMNA VS. ALUMNAE

What’s the difference between alum, alumnus, and alumni?

Quiz yourself on alum vs. alumnus!

Words related to alum

How to use alum in a sentence

British Dictionary definitions for alum

Word Origin for alum

Medical definitions for alum

Scientific definitions for alum