domän

Domén (domain) is a term used across disciplines to denote a defined area, extent, or set of inputs where a concept applies. The specifics vary by field, but the common idea is that a domain marks where rules or properties hold or where a field of activity applies.

In mathematics, the domain of a function is the set of input values for which the function is defined. For example, f(x) = √x has domain x ≥ 0.

In complex analysis, a domain is a nonempty open connected subset of the complex plane. Holomorphic functions are studied on domains, and questions about their behavior depend on factors such as boundary and connectivity.

In computing and networking, a domain often refers to a domain name, a label in the Domain Name System (DNS) that designates an area on the internet, such as example.com. Domains can have subdomains, and DNS translates names to IP addresses.

In biology, protein domains are distinct structural or functional units within proteins that can fold independently and contribute specific activities. Many proteins are modular, combining multiple domains to achieve complex functions.

In other contexts, the domain of discourse in linguistics and logic designates the set of entities under discussion, while the domain of applicability indicates where a model or theorem is valid.