A problem in which all questions take the form ``Is something a member of a particular set?'' and all answers are either ``yes'' or ``no.''

a problem that takes as input some string and requires as output either YES or NO

a problem where all the answers are YES or NO

a problem where the answer is always YES/NO

A problem in which all questions are of the form: "Is the object a member of the set?" and all answers are either "yes" or "no."

A problem for which the desired answer is a single bit (1 or 0, yes or no). For simplicity, theorists often restrict themselves to talking about decision problems.

(n.) a problem whose solution, if any, is found by satisfying a set of constraints.

In computability theory and computational complexity theory, a decision problem is a question in some formal system with a yes-or-no answer. For example, the problem "given two numbers x and y, does x evenly divide y?" is a decision problem. The answer can be either 'yes' or 'no', and depends upon the values of x and y.