Greek Prefixes for Binary Covalent Compounds
| Prefix | Number | Prefix | Number |
| mono- | 1 | hexa- | 6 |
| di- | 2 | hepta- | 7 |
| tri- | 3 | octa- | 8 |
| tetra- | 4 | *nona- | 9 |
| penta- | 5 | deca- | 10 |
Note that the final "o" and "a" are frequently omitted if the prefix is for oxygen so that the name is easier to say.
*Nona- is a Latin prefix.