It likely means "Updated" – users want the latest reprint with corrected problems and additional solved examples.

Happy ε-δ hunting.

| Edition Year | Key Differences | Presence of Solutions | |--------------|----------------|------------------------| | 2003 (1st ed.) | No Lebesgue chapter, black-and-white diagrams | No solutions | | 2010 (2nd ed.) | Added metric spaces, fewer typos | Partial hints (Appendix B) | | 2015 (UPD 1) | Full Riemann-Stieltjes section | 40 solved problems per chapter | | 2018 (UPD 2) | Color-coded theorems, extra exercises from ISI entrance exams | 60% of odd-numbered solved |