Dear Café, What makes "algebraic data types" algebraic? There are at least two common explanations in use: 1. Algebraic data types are defined using sums and products of types, by analogy with, well, concepts from algebra. 2. Algebraic data types are initial algebras. There are numerous blogs online explaining "algebraic data types" that way, with a large majority adopting the more approachable explanation (1). The question is, how did the appellation "algebraic" come about historically? Did it start with one or both of the meanings above? The language feature, independently of the name, seems attributed to the HOPE language[1] (see for instance A History of Haskell: Being Lazy with Class[2]). However, the paper introducing HOPE does not use the word "algebraic" anywhere. Other papers on the topic do not discuss the origins of the word. I am curious about citations regarding the history of the name "algebraic data types" itself. Regards, Li-yao [1]: http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.18.8135 [2]: https://www.microsoft.com/en-us/research/wp-content/uploads/2016/07/history....