std::Semiregular (3) - Linux Man Pages
Defined in header <concepts>
template <class T> (since C++20)
concept Semiregular = std::Copyable<T> && std::DefaultConstructible<T>;
The Semiregular concept specifies that a type is both copyable and default constructible. It is satisfied by types that behave similarly to built-in types like int, except that they need not support comparison with ==.