A person who has signed up for something, like a class or event.
The registrant got a note about the event they signed up for.
注册者收到了他们报名参加的活动的便条。
The owner of a domain name who has the right to use it.
The registrant must keep their domain name active by renewing it.
注册者必须通过续期来保持他们的域名活跃。