ITI9200 - Introduction to Category Theory

What

An introductory course on category theory and its applications; runs at Tallinn University of Technology during the second semester (January to May) of each academic year.

When / Where

Thursday 14.00—15.30 & 16.00—17.30 SOC-313

First lecture: February 5, 2026 / Last lecture: May 21, 2026

Lectures' Log

  • Notes for a computer-science friendly version of the course (link)
  • 0: Introductions, introduction, organization (link)
  • 1: Monoids, posets, categories I (link)
  • 2: Monoids, posets, categories II (link)
  • 3: Functors and natural transformations I (link)
  • 4: Functors and natural transformations II (link)
  • 5: Universal properties I (link)
  • 6: Universal properties II (link)
  • 7: Limits and colimits I (link)
  • 8: Limits and colimits II (link)
  • 9: Adjunctions I (link)
  • 10: Adjunctions II (link)
  • 11: Monads I (link)
  • 12: Monads II (link)

Exercises

For the mind

Warning: this set of exercises is not meant as part of the course, its content is extremely volatile in some parts, and it is usually addressed to people who already have a decent mathematical exposition.

The chapter may cause serious damage to the unwary and/or unprepared reader (implying such damage has not already been caused by the lectures…).

For the exam

Through the course (more or less every other week) I will publish a document with 3-4 exercises; you have until the next sheet to solve them. They are part of you final grade. Deadlines are flexible; if the only problem is that you need more time, just tell me.

  • Sheet 1 PDF (Deadline: Feb 26, 2026)
  • Sheet 2 PDF (Deadline: Mar 19, 2026)
  • Sheet 3 PDF (Deadline: TBA)
  • Sheet 4 PDF (Deadline: TBA)
  • Sheet 5 PDF (Deadline: TBA)

Grading

Your final grade will be determined based on how well you perform on the exercise sheets handed through the course, and a final oral exam. No one stops you from using a robot to learn; embrace the future. But: we are going to have a problem if you come at the whiteboard clueless on how to solve the exercises “you” did.

For the final exam, you can choose a topic from a list, and give a (~30 min+questions) presentation about it. It can relate category theory to whatever you like (one year the link was “monads in functional programming” + supercollider, I dare you to do something cooler than that).

References

All these references are freely available on the internet. If you need more, ask and ye shall receive.
  • Leinster, Basic Category Theory (PDF)
  • Riehl, Category Theory in Context (PDF)
  • Barr and Wells, Category Theory for Computing Science (PDF)
  • Adámek-Herrlich-Strecker, Abstract and concrete categories: the joy of cats (PDF)
  • Awodey, Category Theory (PDF)
footer image

Victor Brauner, Arche-chat, 1948 — Herbert F. Johnson Museum of Art.