admissible
Allowed or acceptable because it follows the rules.
Admissible means allowed or acceptable according to specific rules or standards. In a courtroom, admissible evidence is information that a judge permits the jury to consider, like a photograph of where a crime happened or testimony from a witness who saw what happened. Not all evidence is admissible: a lawyer can't present rumors they heard from someone else because that violates the rules of evidence.
Think of it like a ticket that grants you entry somewhere: admissible evidence gets admitted into the trial, while inadmissible evidence gets turned away at the door.
Outside of courtrooms, admissible describes anything that meets the requirements for acceptance. A late homework assignment might not be admissible if the teacher's policy requires work by a certain deadline. When your debate team considers arguments for an upcoming competition, you discuss which points are admissible under the debate rules and which ones aren't allowed.
The opposite is inadmissible: something that doesn't meet the standards and therefore can't be accepted. Understanding what's admissible means knowing the rules of whatever system you're working within, whether that's a court of law, a school policy, or the regulations of a competition.