Some people insist that admittance should be used only to refer to achieving physical access to a place (He was denied admittance to the courtroom) and that admission should be used to refer to achieving entry to a group or institution (her admission to the club, China’s admission to the United Nations). There is no harm in observing this distinction, but don’t be surprised if you see others ignoring it, for many people do. Admission is much more common in the sense “a fee paid for the right of entry”: The admission to the movie was five dollars.
