In law:

Confession, generally.

University and college admissions

Admissibility is an attribute of evidence (law)

Changes in status allowing an entity to become part of a group, see List of U.S. states by date of statehood

Admission to the bar, change in status allowing an applicant to become part of a profession

Admission (law), a statement that may be used in court against the person making it.

Ticket to enter an event or movie theater

Admittance, an electrical engineering term - the admittance (Y) is the inverse of the impedance (Z).