Suslin's hypothesis is a statement in set theory that concerns the structure of certain types of sets, specifically well-ordered sets. It posits that every well-ordered set that is not finite must contain an uncountable subset that is also well-ordered. This means that if you have a large enough set, you can find a smaller part of it that still has a well-defined order. The hypothesis is named after the mathematician Mikhail Suslin, who introduced it in the early 20th century. It is closely related to the study of cardinal numbers and the continuum hypothesis, which deals with the sizes of infinite sets. Suslin's hypothesis remains independent of the standard axioms of set theory, meaning it cannot be proven or disproven using them.