This is the 379th most frequent Icelandic word.
gildir
"Valid" or "applies."
In this sentence, "gildir" is used as a verb meaning "applies." It shows that the rule is relevant or in effect for everyone.
Reglan gildir fyrir alla.
The rule applies to everyone.
Here, "gildir" expresses the state of being valid or validness. It indicates that the subject is no longer in effect or applies.
Það gildir ekki lengur.
It is no longer valid.
In this context, "gildir" means "serves" or "counts." It demonstrates that the subject is regarded as serving the function of proof.