Alum vs alum

Alum and alum  are two words that are spelled identically but are pronounced differently and have different meanings, which makes them heteronyms. These word pairs are often misused words. Heteronyms exist because of our ever-changing English language, and these words with the same spelling and different pronunciation and meaning are a challenge for those who wish to learn […]
from Grammarist
https://grammarist.com/heteronyms/alum-vs-alum/