Definition

1. Noun:
   • A chemical compound: A double sulfate salt, typically of aluminum with potassium or ammonium, used historically and industrially as an astringent, in water purification, dyeing, and tanning.
   • An informal term for a graduate: A person who has received a degree from a specific school, college, or university.

Usage and Examples

• Noun (Chemical Compound):
  • The traditional recipe uses alum to make the pickles crisp.
  • Alum was a common mordant for fixing dyes to fabric.
• Noun (Graduate):
  • As an alum of the university, she receives regular newsletters.
  • The network of alums from that high school is very strong.

Advanced Usage and Notes

• The chemical term is formal and technical. The informal term for a graduate is a clipped form of "alumnus" (male) or "alumna" (female). The plural forms are "alumni" (mixed or male group) and "alumnae" (female group).
• "Alum" as a graduate: This usage is predominantly North American and informal. In formal contexts, "alumnus/alumna" is preferred.
  • Informal: We're having an alum reunion.
  • Formal: He is a distinguished alumnus of the law school.

Variants and Related Words

• Alumnus (n, singular, male): A male graduate or former student of a particular school.
• Alumna (n, singular, female): A female graduate or former student of a particular school.
• Alumni (n, plural): Graduates or former students, especially of a university (can refer to a mixed-gender or all-male group).
• Alumnae (n, plural): Female graduates or former students.
• Aluminous (adj): Containing alumina or alum.

Synonyms

• For the chemical: Potassium aluminum sulfate; ammonium aluminum sulfate.
• For the graduate: Graduate; former student; graduate member (of an institution).

Related Phrases and Idioms

• Alum list: A list of an institution's graduates.
  • Her name is on the alum list from 2010.
• Alum association/chapter: An organization for graduates of a school.
  • The Boston alum chapter is hosting an event.

Noun

1. a double sulphate of aluminum and potassium that is used as an astringent (among other things)
2. a person who has received a degree from a school (high school or college or university)
3. a white crystalline double sulfate of aluminum: the potassium double sulfate of aluminum
4. a white crystalline double sulfate of aluminum: the ammonium double sulfate of aluminum