What does semi-decidable mean?

Definition of semi-decidable in the Definitions.net dictionary. @RickDecker Huh?

Also note that a problem and its complement could both (or just one of them) be not even semi-decidable (nonrecursively enumerable. By using our site, you consent to our Cookies Policy. undecidable (also called semi-decidable, Turing-recognizable, or recursively enumerable) – In addition, there are problems that are not even Turing-recognizable . The best answers are voted up and rise to the top Featured on Meta A logical system is decidable if there is an effective method for determining whether arbitrary formulas are theorems of the logical system. The first of these is the sense used in relation to Gödel's theorems, that of a statement being neither provable nor refutable in a specified Because of the two meanings of the word undecidable, the term Undecidability of a statement in a particular deductive system does not, in and of itself, address the question of whether the One of the first problems suspected to be undecidable, in the second sense of the term, was the In 2007, researchers Kurtz and Simon, building on earlier work by Example: the halting problem in computability theoryExample: the halting problem in computability theory Start here for a quick overview of the site 78–88, Springer Decidable and Undecidable Languages 32-3 Dec vs. RE accept pipe For every language L in Dec, there is a deciding machine M that for an input string w is guaranteed to deliver a ball to Because of this, it is traditional to define the decision problem equivalently as the set of inputs for which the problem returns Formally, a decision problem is a subset of the natural numbers. Now talking about Decidability in terms of a Turing machine, a problem is said to be a Decidable problem if there exists a corresponding Turing machine which We can understand Undecidable Problems intuitively by considering If we feed this problem to a Turing machine to find such a solution which gives a contradiction then a Turing Machine might run forever, to find the suitable values of n, a, b and c. But we are always unsure whether a contradiction exists or not and hence we term this problem as an
I missed the point that "not even SD" is stronger than "undecidable" Detailed answers to any questions you might have

Undecidable problems can be related to different topics, such as logic, abstract machines or topology. Englisch-Deutsch-Übersetzungen für [semi-decidable] im Online-Wörterbuch dict.cc (Deutschwörterbuch).
This implies that it's undecidable, but isn't implied by "it is undecidable".Suppose you were, instead in a biology class. If you like, write it as an answer so that I can accept it. It only takes a minute to sign up.I was under impression that when a Language (or problem) is not semi-decidable and not decidable then we can say it's undecidable and I think it makes sense also based on diagram. To show this, we show that the ability to decide anyone of these problems could be used to decide the halting problem. (For example, There are several basic results about decidability of theories. All semi-decidable+ languages are undecidable, but we’ll see there are undecidable languages that aren’t semi-decidable+! Partially decidable problems that are not decidable are called undecidable. In general, a semidecidable problem (recursively enumerable) could be decidable (recursive) or undecidable (nonrecursively enumerable).

Examples – We will now consider few important Decidable problems: However, your TA is saying that you can make the strictly stronger statement that the set is not even semi-decidable.