There are 11 words that start with 'opso'.
| opsonic | opsonin | opsonify |
| opsonins | opsonize | opsonized |
| opsonizes | opsonified | opsonifies |
| opsonizing | opsonifying | |
Note: These 11 words that start with 'opso' are found from the USA & Canada version of the tournament Scrabble word list.