Across
- 3. using only one colour
- 5. train running on a single rail
- 7. voice with one unchanging pitch
- 8. detailed study of one subject
- 9. single eyepiece for one eye
- 10. system ruled by one leader
- 13. word with just one syllable
- 15. obsession with one idea
- 17. exclusive control by one seller
- 18. long speech by one speaker
- 19. marriage to one person
- 21. compound with one oxygen atom
Down
- 1. single ruler of a kingdom
- 2. man living a solitary religious life
- 3. massive structure made of one stone
- 4. single unit that can join to form polymers
- 5. speaking only one language
- 6. design made from one set of initials
- 11. sameness or lack of variety (one repeated thing)
- 12. to do one task at a time
- 14. having one point of focus
- 16. seasonal wind pattern (originally meaning a single season)
- 18. sound coming from one channel
- 19. print or design made as a single unique piece
- 20. relating to monks living a single, simple life