### Errata for 'Algebra - Notes from the Underground' (2021)

Highlighted in red are the needed changes, embedded in text matching the published version and identified by page and position on the page (e.g., `p.10, top'). A bold reference indicates an error in the published version which may be more confusing, such as a missing hypothesis in an exercise.

This list is bound to grow forever. (71 items so far.) The contribution of many readers is gratefully acknowledged.

Last updated: 7/1/24.

• #### Chapter 1

• p.5, middle:

• p.5, bottom:

• p.6, end of section 1.1:

• p.9, bottom:

• p.11, top:

• p.20, Exercise 1.2:

• p.21, Exercise 1.24:

• p.21, Exercise 1.26:

• #### Chapter 2

• p.40, Exercise 2.21:

• #### Chapter 3

• p.41, Definition 3.1, preamble:

• p.41, Definition 3.1, part (ii):

• p.42, top:

• p.42, middle:

• p.46, top:

• p.49, top:

• p.54, middle:

• p.58, Exercise 3.20:

• p.58, Exercise 3.22:

• #### Chapter 4

• p.66, Example 4:22:

• p.70, top:

• p.74, Example 4.43:

• #### Chapter 5

• p.79, Example 5.4:

• p.90, Proof of Theorem 5.37:

• p.94, third paragraph:

• p.103, Exercise 5.10:

• #### Chapter 6

• p.109, Example 6.14:

• p.110, Paragraph following Definition 6.16:

• p.120, Lemma 6.41:

• p.124, Theorem 6.45:

• p.127, Exercise 6.14:

• p.127, Exercise 6.15:

• p.128, Exercise 6.22:

• p.128, Exercise 6.23:

• #### Chapter 7

• p.129, bottom half:

• p.144, footnote:

• p.145, third paragraph:

• p.147, Example 7.37:

• p.148, top:

• p.148, Exercise 7.10:

• p.149, Exercise 7.26:

• #### Chapter 8

• p.154, Definition 8.1:

• p.157, Definition 8.11:

• p.171, Exercise 8.2:

• p.173, Exercise 8.20:

• #### Chapter 9

• p.196, top:

• p.201, Exercise 9.19:

• #### Chapter 10

• p.211, Example 10.15:

• p.212, Theorem 10.18:

• p.215, paragraph preceding Theorem 10.22:

• #### Chapter 11

• p.229, Definition 11.1:

• p.233, Definition 11.13:

• p.261, Example 11.71:

• p.266, Exercise 11.34:

• #### Chapter 12

• p.276, Example 12.27:

• p.291, Exercise 12.20:

• #### Chapter 13

• p.306, bottom:

• #### Chapter 14

• p.322, Example 14.7:

• #### Chapter 15

• p.353, bottom:

• p.374, Exercise 15.3:

• p.353, Exercises 15.4 and 15.5:

• #### Appendix A

• p.391, Example A14:

• p.400, second-to-last bullet point:

• p.400, last bullet point:

• #### Appendix B

• p.404, Exercise 1.26:

• p.407, Exercise 3.14:

• p.409, Exercise 4.19:

• p.422, Exercise 7.26, first paragraph:

• p.422, Exercise 7.26, second paragraph:

• p.456, Exercise 15.3:

• p.457, top:

• p.457, Exercise 15.4: