Domain (computing)
Etymology
From Latin "dominium," ownership or lordship — the same root as dominion. A domain was long a territory one ruled, and online it became a named territory one registers and controls. The Domain Name System, introduced in 1983, works like a directory that translates these names into the numeric IP addresses computers route by.
noun · /doh-MAYN/
The human-readable name of a website, like example.com, that stands in for its numerical address.
What it names
The web's real estate: memorable names people can own, type, and trust instead of raw strings of numbers.
Example
Squatters had already bought the domain, so the startup had to rename itself.
Related idea
A domain name is the address you own, distinct from the website itself, which is the content it points to — you can keep the domain while completely rebuilding what sits behind it.
noun · /doh-MAYN/
A sphere of knowledge, activity, or authority — the area something belongs to or someone controls.
What it names
It marks the boundary of a field or jurisdiction ('that's outside my domain'), the general sense that the web-address meaning was built on top of.
Example
Questions of tax law are really outside my domain.
Related idea
Close to one's purview or remit — the field or jurisdiction something falls within ('that's outside my domain'), the general sense the web-address meaning was built on top of.
noun · /doh-MAYN/
In mathematics, the complete set of input values a function is allowed to take.
What it names
The ‘legal inputs’ of a function — everything you may feed in — paired with the range of what comes out.
Example
The function 1/x has a domain of all real numbers except zero.
Related idea
Domain is the set of inputs; range is the set of outputs. Both are precise mathematical sets, unlike the loose ‘sphere of activity’ sense (a domain of expertise).
noun · /doh-MAYN/
The realm of creative works free from copyright, which anyone may use without permission.
What it names
The shared commons of expired or unclaimed works — what belongs to everyone rather than to any owner.
Example
Shakespeare’s plays are in the public domain, so anyone can reprint them.
Related idea
This is the flip side of copyright: where copyright reserves control to a creator, the public domain is the pool of works that control has lapsed on or never covered.