An Etymological Dictionary of Astronomy and Astrophysics

1. An act of entering, as into a place or upon new duties.
   

2. A point or place of entering; an opening or passage for entering, as a doorway (Dictionary.com).

→ entrance pupil, → entrance slit.

Etymology (EN): M.E. entraunce, from M.Fr. entrance, from → enter + → -ance.

Etymology (PE): Darâyeš, verbal noun of darâmadan, darâyidan, → enter; darâygâh with space suffix -gâh.