 A maximal compact subgroup of a semisimple Lie group may not be unique, but is unique up to conjugation.An object that is the limit or colimit over a given diagram is essentially unique, as there is a "unique" isomorphism to any other limiting/colimiting object.Given the task of using 24-bit words to store 12 bits of information in such a way that 7-bit errors can be detected and 3-bit errors can be corrected, the solution is essentially unique