Admittance is a noun meaning "the act of permitting entry; the right to enter". Historically, it is from admit + -ance, from Latin admittere ('to let in'), from ad- ('to') + mittere ('to send'). The visible construction is part of the etymology: admittance is not just an unanalyzed simple word. The modern meaning, "the act of permitting entry; the right to enter", follows the base word through the added English ending. The historical chain links Latin admittere with Latin mittere. Close English family members include admit, admission, and admissible.