Jargon: Sum Type, Discriminated Union, Tagged Union, Disjoint Union (2016)

By Xah Lee. Date: . Last updated: .

The jargons {sum type, tagged union, discriminated union, disjoint union} have same meaning but with nuances in different context. (e.g. in math, and in different programing languages.)

Sum Type

sum type 2025-12-23 at 12.51.47
sum type 2025-12-23 at 12.51.47
sum type Wikipedia 2025-12-23 at 12.53.40
sum type Wikipedia 2025-12-23 at 12.53.40

Discriminated Union

sum type discriminated union 2025-12-23 at 12.40.06
sum type discriminated union 2025-12-23 at 12.40.06

Discriminated Union in Fsharp

sum type discriminated union fsharp 2025-12-23 DxkdY
sum type discriminated union fsharp 2025-12-23 DxkdY
sum type discriminated union fsharp 2025-12-23
sum type discriminated union fsharp 2025-12-23

Tagged Union

tagged union 2025-12-23 2348d
tagged union 2025-12-23 2348d

Disjoint Union

sum type disjoint union 2025-12-23
sum type disjoint union 2025-12-23