I saw a tweet that said
And my dictionary translated 呑む as 'to drink', with 飲む as the default spelling and 呑む as an alternate form.
What is the difference between 飲む and 呑む?
Maybe you know that to say "to take a pill" in Japanese you would say 丸薬をのむ. (I did not put the kanji of のむ intentionally).
飲む is used to say to drink. I mean, to absorb a liquid through your mouth like "to drink water, syrup, beer, ..."
On the other side 呑む is used more to mean to swallow. It can be figurative or not. 涙｛なみだ｝を呑｛の｝む (to refrain one's anger), 固唾｛かたず｝を呑む(to hold one's breath because of anxiety/fear), 息を呑む (to gasp). 町は闇に呑まれた (the village was in the dark).
Thus, the "right" spelling of 丸薬をのむ is with 呑む but today everyone uses 飲む (because 呑 is not part of the 常用漢字).