1. inner part; interior; back (of a drawer, one's throat, etc.); depths (e.g. of a forest); recesses (e.g. of a cave); heart; end (of a road, garden, etc.)
2. living quarters (at the back of a house); inner room
3. recesses (of one's mind); bottom (of one's heart); behind (someone's words); mysteries (of an art)
4. wife (of a person of high status)