Each answer has 4 letters, but 3 of those letters are vowels.
1. A currency
2. A genus containing over 500 species of flowering succulent plants, some used in skin care products
3. A US state
 Ohio (or Iowa)
4. Instead
5. Goodbye
6. The chief component of urine
7. A larval form of crabs and certain other crustaceans, characterised by thoracic appendages used for swimming
8. A man who is the lover of a girl
9. A US state (but not the one in Question 3!)
 Iowa (or Ohio)
10. 9th letter of the Greek alphabet