# Applied Category Theory Course from 2018 Still Relevant

Hacker News is highlighting a 2018 online course on applied category theory, which teaches how to use categorical structures to model real-world systems in fields like physics, computer science, and engineering. The course remains valuable for mathematicians and programmers seeking to understand compositional reasoning and abstraction. This matters because category theory is increasingly central to modern data science and programming language theory.

**Importance:** 2/5

## Sources

### Technology
- [Hacker News](https://math.ucr.edu/home/baez/act_course/index.html) — Fri, 03 Jul 2026 20:42:00 +0000