Number prefixes

12345678910
Across
  1. 2. a drawing in different shades of one color
  2. 5. twice a month
  3. 7. an athletic contest with five events
  4. 9. a group of eight musicians or singers
  5. 10. polygon with five sides
Down
  1. 1. single stone structure, obelesk
  2. 3. sea creature with eight arms
  3. 4. arranged in a half circle
  4. 6. every half a year, twice yearly
  5. 8. the shape of a stop sign