(number theory) The problem of whether each natural number k has an associated positive integer s such that every natural number is the sum of at most s natural numbers raised to the power k.

(computing) The problem of how to create a superintelligent AI whose values would align with the interests of humankind.

(philosophy) A thought experiment, asking, "if a man born blind can feel the differences between shapes such as spheres and cubes, could he, if given the ability to see, distinguish those objects by sight alone, in reference to the tactile schemata he already possessed?"

A type of thought experiment in ethics and psychology, involving ethical dilemmas of whether to sacrifice one person to save a larger number.

(mathematics) The problem of finding integer values of n and m for which n!+1=m², where n! is the factorial.

(philosophy) A problem arising from the tension between the seemingly irreducible nature of consciousness, and its ubiquity. If consciousness is ubiquitous, and every atom (or every bit, depending on the theory) has a minimal level of it, then it is not clear how these tiny consciousnesses combine to create larger experiences.

(creationism, pseudoscience) The conflict between Young Earth creationism (asserting that the universe is thousands of years old) and the starlight-related measurements that show the universe to be billions of years old.

Alternative spelling of subproblem

An insignificant problem of a privileged person.

(mathematics) The problem of generalizing Paul Gordan's computational approach to the theorem of the finiteness of generators for binary forms to work with functions having more than two variables.