The answers to the clues below will have something in common.

1. Holy Communion in the Catholic Church
2. One of seven
3. City in Oregon
4. "Father of geometry"
5. One of two Mesopotamian rivers
6. Feeling of exultation
7. Panda bear's favorite tree
8. Greek playwright of the Golden Age
9. Funeral tribute
10. Restroom, for one
11. Word on the California state seal

Answers:

1. Eucharist
2. Europe
3. Eugene
4. Euclid
5. Euphrates
6. Euphoria
7. Eucalyptus
8. Euripedes
9. Eulogy
10. Euphemism
11. Eureka 

Credit: 
NPR Weekend Edition Sunday Puzzle
February 12, 2011 
Will Shortz